H1N1 Flu (Swine Flu) Канада
Symptoms of Swine Flu (H1N1 Flu)
Symptoms of swine flu, which is caused by the H1N1 virus, are like those of any seasonal flu and include fever, cough, runny nose, sore throat, body aches, chills, and fatigue. Although some people still talk about swine flu, it’s important to keep in mind that now swine flu is considered another regular type of human flu virus, similar to other seasonal flu viruses.
In 2009, the big difference was that when the swine influenza A virus known as H1N1 first appeared, it was new and most people d > Now this strain is included in the annual flu vaccine.
Like other seasonal flu viruses, common symptoms of swine flu (H1N1) develop between one and three days after you’ve been infected and can include:
- Fever, which is usually high, but is sometimes absent
- Runny or stuffy nose
- Sore throat
- Body aches
- Fatigue or tiredness, which can be extreme
- Diarrhea and vomiting occasionally, but more commonly seen than with other strains of flu
The H1N1 strain is now included in seasonal influenza vaccines.
Serious symptoms are rarer. In children, they can include:
- Fast breathing or difficulty breathing
- Bluish or gray skin color
- Not drinking enough fluids
- Severe or persistent vomiting
- Not waking up or not interacting
- Irritability so great that your child does not want to be held
- Flu-like symptoms get better but then come back with fever and worse cough
- Rash with a fever
In adults, serious symptoms include:
- Difficulty breathing
- Chest pain or pressure
- Abdominal pain or pressure
- Vomiting that’s severe or won’t stop
- Flu-like symptoms get better but then come back with fever and worse cough
If you notice these, don’t panic right away. It’s important to coordinate with a doctor or your medical team for prompt attention, and they can help you resolve the issue and its underlying cause.
Most people who get swine flu recover within a few days to two weeks after first having symptoms, but some people may develop complications.
H1N1 complications are most likely to occur if you:
- are pregnant
- are younger than 5 or older than 65 years old
- have a chronic illness such as asthma, emphysema, diabetes, or heart disease
Potential complications include:
- Worsening of a chronic condition
- Ear infection
- Respiratory failure
When to See a Doctor
Most normally healthy people can recover from the flu at home and prevent spreading it by avoiding other people. However, if you have a chronic illness like asthma, diabetes, or heart disease or have a suppressed immune system and you think you have the flu, you should see your doctor so he or she can properly diagnose you and treat your symptoms accordingly.
You may get a course of antiviral medications that are used for high-risk people to help lessen the length and severity of your illness.
H1N1 Swine Flu Doctor Discussion Gu > Get our printable guide for your next doctor’s appointment to help you ask the right questions.
You should seek emergency care if you or your child has any of the serious symptoms listed above and/or you’re getting worse. This is especially true if you or your child has a chronic illness as well.
When to Seek Emergency Care for Infants
If your baby has the flu and the following symptoms occur, seek emergency care immediately.
- Unable to eat
- No tears when crying
- Having difficulty breathing
- Fewer wet diapers than normal
The flu can be a life-threatening disease for children, especially those 5 years of age and younger, people over 65, and those with chronic conditions, so getting medical care as soon as possible for these populations is important.
What is the pandemic (H1N1) 2009 virus?
24 February 2010
This is an influenza virus that had never been identified as a cause of infections in people before the current H1N1 pandemic. Genetic analyses of this virus have shown that it originated from animal influenza viruses and is unrelated to the human seasonal H1N1 viruses that have been in general circulation among people since 1977.
Antigenic analysis has shown that antibodies to the seasonal H1N1 virus do not protect against the pandemic H1N1 virus. However, other studies have shown that a significant percentage of people age 65 and older do have some immunity against the pandemic virus. This suggests that some people in the older age group may have some cross protection from exposure to viruses that have circulated in the more distant past.
After early outbreaks in North America in April 2009 the new influenza virus spread rapidly around the world. By the time WHO declared a pandemic in June 2009, a total of 74 countries and territories had reported laboratory confirmed infections. To date, most countries in the world have confirmed infections from the new virus.
Unlike typical seasonal flu patterns, the new virus caused high levels of summer infections in the northern hemisphere, and then even higher levels of activity during cooler months in this part of the world.
The new virus has also led to patterns of death and illness not normally seen in influenza infections. Most of the deaths caused by the pandemic influenza have occurred among younger people, including those who were otherwise healthy. Pregnant women, younger children and people of any age with certain chronic lung or other medical conditions appear to be at higher risk of more complicated or severe illness. Many of the severe cases have been due to viral pneumonia, which is harder to treat than bacterial pneumonias usually associated with seasonal influenza. Many of these patients have required intensive care.
How do people become infected with the virus?
The pandemic H1N1 virus is spread from person to person, similar to seasonal influenza viruses. It is transmitted as easily as the normal seasonal flu and can be passed to other people by exposure to infected droplets expelled by coughing or sneezing that can be inhaled, or that can contaminate hands or surfaces.
To prevent spread, people who are ill should cover their mouth and nose when coughing or sneezing, stay home when they are unwell, clean their hands regularly, and keep some distance from healthy people, as much as possible.
What are the signs and symptoms of typical infection?
Signs of the pandemic influenza are flu-like, including malaise, fever, cough, headache, muscle and joint pain, sore throat and runny nose, and sometimes vomiting and diarrhoea.
The majority of people with pandemic influenza experience mild illness and recover fully without treatment.
When should someone seek medical care?
People should seek medical care if they experience shortness of breath or difficulty breathing, or if a fever, and especially high fever, continues more than three days. For parents with a young child who is ill, seek medical care if a child has fast or labored breathing, continuing fever or convulsions (seizures).
Supportive care at home — resting, drinking plenty of fluids and using a pain reliever for aches and pains — is adequate for recovery in most cases. A non-aspirin pain reliever should be used for children or adolescents under age 18.
Why was WHO so worried about this flu when hundreds of thousands die every year from seasonal epidemics?
Seasonal influenza occurs every year and the viruses change each year — but many people have some immunity to the circulating virus that helps limit infections. Some countries also use seasonal influenza vaccines to reduce illness and deaths.
By contrast, the pandemic H1N1 was a new virus when it emerged and most people had no or little immunity to it. In addition, one of the lessons from history is that influenza pandemics can kill millions. Finally, there was no pandemic influenza vaccine at the outset.
The global impact of the current pandemic has not yet been estimated. Typically, the numbers of deaths from seasonal influenza or past pandemics are estimated using statistical models.
By contrast, the currently reported counts of over 16,000 deaths from pandemic H1N1 represent individually tested and confirmed deaths, primarily reported from countries with adequate resources for widespread laboratory testing. This approach has never been used to count seasonal or previous pandemic deaths and results in a significant underestimate.
A more accurate assessment of mortality from the pandemic, using statistical models, will likely be possible in about one to two years.
The 2009 H1N1 Pandemic: Summary Highlights, April 2009-April 2010
On this Page
Updated: June 16, 2010
This document summarizes key events of the 2009 H1N1 pandemic and CDCвЂ™s response activities for historical purposes. This document is a summary; it is not a comprehensive account of all CDC actions and activities nor is it intended to represent response efforts by other agencies and partners.
Pandemic Preparedness, Background
The 2009 H1N1 influenza (flu) pandemic occurred against a backdrop of pandemic response planning at all levels of government including years of developing, refining and regularly exercising response plans at the international, federal, state, local, and community levels. At the time, experts believed that avian influenza A (H5N1) viruses posed the greatest pandemic threat. H5N1 viruses were endemic in poultry in parts of the world and were infecting people sporadically, often with deadly results. Given that reality, pandemic preparedness efforts were largely based on a scenario of severe human illness caused by an H5N1 virus. Despite differences in planning scenarios and the actual 2009 H1N1 pandemic, many of the systems established through pandemic planning were used and useful for the 2009 H1N1 pandemic response.
CDCвЂ™s response to the 2009 H1N1 pandemic response was complex, multi-faceted and long-term, lasting more than a year. This document seeks to document for the public the key events of the pandemic as they unfolded and CDCвЂ™s response. The following is a summary narrative of highlighted CDC-related events from the 2009 H1N1 pandemic.
A Virus Emerges
2009 H1N1 was first detected in the United States in April 2009. This virus was a unique combination of influenza virus genes never previously identified in either animals or people. The virus genes were a combination of genes most closely related to North American swine-lineage H1N1 and Eurasian lineage swine-origin H1N1 influenza viruses. Because of this, initial reports referred to the virus as a swine origin influenza virus. However, investigations of initial human cases did not identify exposures to pigs and quickly it became apparent that this new virus was circulating among humans and not among U.S. pig herds.
Infection with this new influenza A virus (then referred to as вЂswine origin influenza A virusвЂ™) was first detected in a 10-year-old patient in California on April 15, 2009, who was tested for influenza as part of a clinical study. Laboratory testing at CDC confirmed that this virus was new to humans. Two days later, CDC laboratory testing confirmed a second infection with this virus in another patient, an 8-year-old living in California about 130 miles away from the first patient who was tested as part of an influenza surveillance project. There was no known connection between the two patients. Laboratory analysis at CDC determined that the viruses obtained from these two patients were very similar to each other, and different from any other influenza viruses previously seen either in humans or animals. Testing showed that these two viruses were resistant to the two antiviral drugs amantadine and rimantadine, but susceptible to the antiviral drugs oseltamivir and zanamivir. CDC began an immediate investigation into the situation in coordination with state and local animal and human health officials in California.
The cases of 2009 H1N1 flu in California occurred in the context of sporadic reports of human infection with North American-lineage swine influenza viruses in the United States, most often associated with close contact with infected pigs. (During December 2005 вЂ“ January 2009, 12 cases of human infection with swine influenza were reported; five of these 12 cases occurred in patients who had direct exposure to pigs, six patients reported being near pigs, and the source of infection in one case was unknown). Human-to-human spread swine influenza viruses had been rarely documented and had not been known to result in widespread community outbreaks among people. In mid-April of 2009, however, the detection of two patients infected with swine origin flu viruses 130 miles apart, raised concern that a novel swine-origin influenza virus had made its way into the human population and was spreading among people.
CDC remained in close contact with the international health community as the outbreak unfolded and on April 18, 2009, under the International Health Regulations (IHR) the United States International Health Regulations Program reported the 2009 H1N1 influenza cases to the World Health Organization (WHO). The cases also were reported to the Pan American Health Organization (PAHO), Canada and Mexico, as part of the Security and Prosperity Partnership of North America.
Response Ramps Up
CDC worked closely with state and local animal and human health officials on epidemiological investigations by tracing contacts of both patients to try to determine the source of their infection and by examining whether there was any link between the patients and pigs. Surveillance also was enhanced to try to detect additional cases of human illness with this virus. Based on the geographic location of the first cases, lack of contact between these cases and swine, and data collected through contact tracing and laboratory testing, CDC epidemiologists suspected that human-to-human transmission of this virus had taken place. In an article entitled Swine Influenza A (H1N1) Infection in Two Children — Southern California, March-April 2009 published on April 21, 2009 in the Morbidity and Mortality Weekly Report (MMWR), CDC described the cases and requested that state public health laboratories send to CDC all influenza A specimens that could not be subtyped. That same day CDC responded to media inquiries related to the MMWR from medical reporters. Within a day, three additional samples of this new virus were identified in San Diego County and Imperial County California hospitals and sent to CDC for further testing. CDC laboratory testing confirmed that these samples also were positive for the virus that would come to be called вЂњ2009 H1N1.вЂќ
By April 21, 2009, CDC had begun working to develop a virus that could be used to make vaccine to protect against this new virus (called a candidate vaccine virus). There are many steps involved with producing a vaccine вЂ“ the first step is getting a good high yield vaccine virus. A high-yield vaccine virus is a sample of the virus that is used to grow the virus in mass quantities in chicken eggs. Once the virus is grown in mass quantities, the virus particles are then purified to make vaccine. Recognizing that 2009 H1N1 was a new flu virus вЂ“ and, like all flu viruses, unpredictable — CDC simultaneously pursued multiple scientific methods to create a high-yield virus. A virus isolated at CDC, (called A/California/07/2009) was eventually chosen to be the vaccine virus used to make vaccine. CDC sent the vaccine virus to vaccine manufacturing companies so that they could begin vaccine production, in the event that the U.S. government should decide a vaccine was necessary.
CDC activated its Emergency Operations Center (EOC) on April 22, 2009, to coordinate the response to this emerging public health threat. Response activities were organized into a team structure according to the National Incident Management System (NIMS)These teams had different areas of focus including but not limited to: surveillance, laboratory issues, communications, at-risk populations, antiviral medications, vaccine, and travelerвЂ™s health issues. As the outbreak unfolded, team structures and staffing were periodically assessed for functionality and utility.
On April 23, 2009, samples submitted by Texas revealed two additional cases of human infections with 2009 H1N1, transforming the investigation into a multistate outbreak and response. At the same time, CDC was testing 14 samples from Mexico, some of which had been collected from patients who were ill before the first 2 U.S. (California) patients. Results from seven of the samples were positive for 2009 H1N1 and similar findings were reported for specimens submitted by Mexico to Canada. It had now become clear that cases were occurring in multiple countries and human to human spread of the virus appeared to be ongoing. That same day CDC held the first formal full press briefing to inform the media and guide the public and health care response to the rapidly evolving situation. CDC held nearly 60 press briefings during the 2009 H1N1 response.
On April 24, 2009, CDC uploaded complete gene sequences of the 2009 H1N1 virus to a publicly-accessible international influenza database, which enabled scientists around the world to use the sequences for public health research and for comparison against influenza viruses collected elsewhere, and an updated report on the outbreak was published online in the MMWR.
World Braces for Possible Pandemic
On Saturday, April 25, 2009, under the rules of the International Health Regulations, the Director-General of WHO declared the 2009 H1N1 outbreak a Public Health Emergency of International Concern and recommended that countries intensify surveillance for unusual outbreaks of influenza-like illness and severe pneumonia. Also on April 25, 2009, New York City officials reported an investigation into a cluster of influenza-like illness in a high school, and CDC testing confirmed two cases of 2009 H1N1 influenza infection in Kansas, and another case in Ohio shortly after.
On April 26, 2009, the United States Government determined that a public health emergency existed nationwide; CDCвЂ™s Strategic National Stockpile (SNS) began releasing 25% of the supplies in the stockpile that could be used to protect and treat influenza. This included 11 million regimens of antiviral drugs, and personal protective equipment including over 39 million respiratory protection devices (masks and respirators), gowns, gloves and face shields, to states (allocations were based on each stateвЂ™s population).
As part of the nationвЂ™s pre-pandemic planning efforts, by April 2009 the Federal Government had purchased 50 million treatment courses of antiviral drugs вЂ“ oseltamivir and zanamivir вЂ“ for the SNS, and states had purchased 23 million antiviral regimens. After the determination of the public health emergency, FDA also took action to expand possible usage of antiviral drugs oseltamivir and zanamivir by issuing Emergency Use Authorizations (EUAs).
The EUAs allowed for use of the products in a manner different from what they were FDA-approved for. This included allowing for off-label use of:
- oseltamivir to treat children younger than 1 year of age and to help prevent influenza in children 3 months to 1 year of age, and;
- oseltamivir and zanamivir to treat patients who are symptomatic for more than two days before initiation of treatment, or who had complicated illness requiring hospitalization.
On April 27, the WHO Director-General raised the level of influenza pandemic alert from phase 3 to phase 4, based primarily on epidemiological data demonstrating human-to-human transmission and the ability of the virus to cause community-level outbreaks. Based on reports of widespread influenza-like-illness and many severe illnesses and deaths in Mexico, CDC issued a travel health warning recommending that United States travelers postpone all non-essential travel to Mexico. As in past influenza seasons, CDC urged the public and especially those people at highest risk of influenza-related complications, to protect themselves by taking antiviral drugs early in their illness when recommended by their doctor; CDC also advised that everyone take every day preventive actions like covering coughs and sneezes and staying home from work and school when ill to help reduce the spread of illness.
On April 29, 2009 WHO raised the influenza pandemic alert from phase 4 to phase 5, signaling that a pandemic was imminent, and requested that all countries immediately activate their pandemic preparedness plans and be on high alert for unusual outbreaks of influenza-like illness and severe pneumonia. The U.S. Government was already implementing its pandemic response plan. CDC continued to post and update guidance for states, clinicians, laboratories, schools, partners and the public on topics ranging from the non-pharmaceutical measures communities could take to limit spread of disease, to how to evaluate a patient for possible infection with 2009 H1N1 influenza, to how to care for children who might be sick with 2009 H1N1 influenza.
On April 30, 2009, CDC issued an MMWR Dispatch describing the initial outbreak of 2009 H1N1 influenza in Mexico. Findings in Mexico indicated that transmission in Mexico involved person-to-person spread with multiple generations of transmission. CDC also issued an MMWR Dispatch on the outbreak of 2009 H1N1 influenza infection in a high school in New York City, that was, at the time, the largest reported cluster of 2009 H1N1 cases in the United States. The Dispatch suggested that the high school age students had respiratory and fever symptoms similar to those caused by a seasonal flu, but in addition, about half had diarrhea, which is more than expected with seasonal flu. As the details of the outbreak unfolded, the Federal response continued in high gear. Also on April 30, 2009, HHS announced that the Federal government would purchase an additional 13 million treatment courses of antiviral drugs to help fight influenza. The additional treatment courses would be added to the SNS.
As the outbreak spread, CDC began receiving reports of school closures and implementation of community-level social distancing measures meant to slow the spread of disease. School administrators and public health officials were following their pandemic plans and doing everything they could to slow the spread of illness. (Social distancing measures are meant to increase distance between people. Measures include staying home when ill unless to seek medical care, avoiding large gatherings, telecommuting, and implementing school closures).
CDC Laboratories Bolster NationвЂ™s Testing Capacity
While initial efforts were underway to develop a safe and effective vaccine to protect people against 2009 H1N1, work also was being done at CDC to help laboratories supporting health care professionals to more quickly identify the 2009 H1N1 virus in samples from patients. The real-time PCR test developed by CDC was cleared for use by diagnostic laboratories by FDA under an Emergency Use Authorization (EUA) on April 28, 2009, less than two weeks after identification of the new pandemic virus. Prior to the availability of this EUA, public health laboratories had been able to identify whether influenza A viruses were seasonal influenza viruses or were a novel strain, but the new diagnostic kits allowed labs to confirm a virus as 2009 H1N1. On May 1, 2009, CDC test kits began shipping to domestic and international public health laboratories. (Each test kit contained reagents to test 1,000 clinical specimens). From May 1 through September 1, 2009, more than 1,000 kits were shipped to 120 domestic and 250 international laboratories in 140 countries. Once labs had the test kits and verified that their testing was running properly, they were able to identify new cases more quickly than before and no longer needed to send samples to CDC for lab confirmation. The transition away from CDC lab confirmation testing didnвЂ™t happen overnight though — between April 23 and May 31, 2009, CDC influenza laboratory analyzed about 5,000 influenza virus samples, five times the number that were processed in a similar timeframe in 2008, and more than during any previous influenza season. By May 18, 2009, 40 states had been validated to conduct their own 2009 H1N1 testing, with eight states having multiple laboratories able to do their own testing. CDC alerted the public that the expansion in testing capacity would likely result in a jump in the number of 2009 H1N1 cases, but that this would actually present a more accurate picture of the true scope of 2009 H1N1 influenza in the United States.
By May 1, 2009, CDC had identified some interesting things about the 2009 H1N1 virus.
- Researchers had confirmed earlier testing that the 2009 H1N1 influenza virus was a quadruple-reassortant virus, meaning that it contained virus genes that originated from four different influenza virus sources. Some of the gene segments originated from North American swine influenza viruses, some gene segments originated from North American avian influenza viruses, one gene segment originated from a human influenza virus, and two gene segments were normally found in swine influenza viruses from Asia and in Europe.В
- Testing of a number of the virus samples submitted to CDC showed that they were very similar, which means they likely originated from the same source.В
- Laboratory testing showed that the 2009 H1N1 influenza virus did not have any 1918-like markers that had been associated with increased risk of severe disease.В
- Testing also did not find genetic markers that were previously associated with high death rates in people infected with the avian influenza A (H5N1) virus in other countries.В
On May 4, 2009, CDC shifted from reporting confirmed cases of 2009 H1N1 to reporting both confirmed and probable cases of 2009 H1N1. At that point, more than 98% of вЂњprobableвЂќ flu virus samples were testing positive for 2009 H1N1, indicating the ever-growing scale of the outbreak. Probable cases were reported to CDC by state health departments and occurred in people who tested positive for influenza A and negative for seasonal influenza A(H1N1) and A(H3N2) subtypes at their state health department laboratory, but whose samples had not had confirmatory testing for the 2009 H1N1 influenza virus.
CDC deployed a large number of staff to the field to support the outbreak response; by May 1, 2009, 50 staff people were deployed, and that number climbed to more than 100 by May 11, 2009, before gradually declining as field teams returned from deployment to complete studies, analyze collected data, and help inform policy decisions for the prevention and control of 2009 H1N1 influenza. Over the course of the outbreak, more than 3,300 people from throughout CDC would support the response.
On May 6, 2009, CDC distributed recommendations for the use of influenza antiviral medicines to provide guidance for clinicians in prescribing antiviral medicines for treatment and prevention (chemoprophylaxis) of 2009 H1N1 influenza. CDC recommended that testing and antiviral treatment be prioritized for people with severe respiratory illness and people at high risk of complications from seasonal influenza. This included children younger than 5 years old, pregnant women, people with chronic medical conditions, and people 65 years and older.
On May 8, 2009, CDC issued an MMWR updating the situations in Mexico, the United States, and worldwide, and on May 15, 2009, CDCвЂ™s Travel Health Warning recommending against non-essential travel to Mexico, in effect since April 27, 2009, was downgraded to a Travel Health Precaution for Mexico.
By this point in the outbreak, about half of all influenza viruses being detected through laboratory surveillance were 2009 H1N1 viruses, with the other half being regular seasonal influenza viruses, including seasonal influenza A H1N1, influenza A H3N2 and type B viruses. Surveillance reports indicated that the largest number of 2009 H1N1 influenza confirmed and probable cases (about 57% of cases) were occurring among people between 5 years and 24 years of age, and 41% of the hospitalizations were occurring among older children and young adults. The highest rates of hospitalization were among children younger than 5 years of age; the next highest hospitalization rate was in people 5 years to 24 years of age. Based on data from previous influenza pandemics and seasonal influenza, pregnant women had been recognized as a high-risk group early in the outbreak. Early data on 2009 H1N1 illness among pregnant women was reported in an article published as an MMWR Dispatch on May 12, 2009. This article emphasized the importance of empiric treatment (treatment without confirmatory testing) of pregnant women suspected to have 2009 H1N1. People with other previously recognized medical conditions that placed them at high risk of complications from seasonal influenza also appeared to be at increased risk of complications from 2009 H1N1 influenza. In this report, seventy-one percent (71%) of hospitalized patients had one or more underlying chronic medical conditions. Reported deaths had occurred in people ranging in age from 22 months old to 57 years old. Also, only 13% of hospitalizations had occurred in people 50 years and older, and there were few cases and no deaths in people older than 65 years, which was unusual when compared with seasonal flu.
Early results of an antibody study conducted by CDC indicated that children had no existing cross-reactive antibody to the 2009 H1N1 influenza virus, while about one-third of adults older than 60 years of age had cross-reactive antibody against the 2009 H1N1 flu virus. One possible explanation for this pre-existing antibody in older adults was that they may have had previous exposure, either through infection or vaccination, to an influenza A H1N1 virus that was more closely related to the 2009 H1N1 flu virus than contemporary seasonal influenza A (H1N1) viruses are. Data from a similar study suggested that seasonal influenza vaccine would not provide any significant protection against 2009 H1N1 influenza virus.
A Pandemic is Declared
On June 11, 2009, WHO signaled that a global pandemic of 2009 H1N1 influenza was underway by further raising the worldwide pandemic alert level to Phase 6 . That day, CDC held its first press conference with the new CDC Director Thomas Frieden, MD, MPH. The press conference had a total of 2,355 participants. At the time, more than 70 countries had reported cases of 2009 H1N1 infection, and community level outbreaks of 2009 H1N1 were ongoing in multiple parts of the world. The WHO decision to raise the pandemic alert level to Phase 6 was a reflection of spread of the virus in other parts of the world and not a reflection of any change in the 2009 H1N1 influenza virus or associated illness. To date, most people in the United States who had become ill with 2009 H1N1 influenza had not become seriously ill and had recovered without hospitalization.
After the WHO declaration of a pandemic on June 11, the 2009 H1N1 virus continued to spread and the number of countries reporting cases of 2009 H1N1 nearly doubled from mid-June 2009 to early July 2009. Significant levels of 2009 H1N1 illness continued, with localized and in some cases intense outbreaks occurring. By June 19, 2009, all 50 states in the United States, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands had reported cases of 2009 H1N1 infection. The United States continued to report the largest number of 2009 H1N1 cases of any country worldwide, although most people who became ill recovered without requiring medical treatment. By late June more than 30 summer camps in the U.S. had reported outbreaks of 2009 H1N1 influenza illness, and CDC released guidance for day and residential camps to reduce the spread of influenza. At the June 25, 2009 Advisory Committee on Immunization Practices Meeting, CDC estimated that at least 1 million cases of 2009 H1N1 influenza had occurred in the United States.
In early July, 2009, three 2009 H1N1 influenza viruses that were resistant to the antiviral drug oseltamivir were detected in three countries. (Antiviral resistance is when a virus changes in such a way that the antiviral drug is less effective in treating or preventing illnesses caused by the virus.) CDC and WHO partners continued to conduct surveillance for antiviral resistance, although instances of antiviral resistance continued to be detected very rarely.
Also in July 2009, CDC reported findings in the MMWR that indicated a striking prevalence of obesity in intensive care patients who were confirmed to have 2009 H1N1 influenza. Throughout the pandemic, CDC would continue to examine the relationship between 2009 H1N1 influenza, obesity, severe disease and other underlying risk factors.
CDC continued to work with the Council of State and Territorial Epidemiologists (CSTE) to enhance surveillance for 2009 H1N1 influenza. As 2009 H1N1 cases continued to occur through the spring and summer, the task of counting cases became increasingly difficult. On May 12, 2009, CDC transitioned from reporting individual confirmed and probable cases of 2009 H1N1 influenza to reporting aggregate counts of 2009 H1N1 lab confirmed and probable cases, hospitalizations and deaths with the launch of an aggregate reporting web site. Once the numbers of cases increased beyond the point where counting of individual cases was practical, on July 23, 2009, CDC reported the number of 2009 cases for the last time. Reporting of 2009 H1N1 hospitalizations and deaths continued. In addition, CDC continued using its traditional surveillance systems to track the progress of the 2009 H1N1 influenza outbreak. Traditional surveillance systems do not count individual cases, but instead monitor activity levels and virus characteristics through a nationwide surveillance system.
CDC worked closely with countries in the Southern Hemisphere to monitor and enhance surveillance for influenza viruses throughout the summer months. The Southern HemisphereвЂ™s influenza season began in May 2009 and countries there reported that 2009 H1N1 virus was spreading and causing illness along with regular seasonal influenza viruses. After mid-July, disease activity in most countries decreased, and by November, temperate regions of the Southern Hemisphere were reporting very little 2009 H1N1 disease activity. In general, the experience of the Southern Hemisphere with the 2009 H1N1 virus was similar to what is usually seen during a regular influenza season and did not seem to excessively impact the health care systems in the Southern Hemisphere. Also, surveillance systems did not find significant changes in the 2009 H1N1 influenza viruses circulating in the Southern Hemisphere as compared to viruses isolated from people in the Northern Hemisphere. These findings provided the U.S. with valuable clues related to what the 2009-2010 influenza season in the United States might be like. Importantly, the lack of significant changes in the virus indicated that the 2009 H1N1 vaccine being manufactured would closely match the currently circulating 2009 H1N1 viruses and likely provide people with good protection against 2009 H1N1 influenza.
Ongoing Surveillance & Response
2009 H1N1 influenza summer activity peaked in the United States during May and June and declined during July and early August. However, levels of influenza activity would remain above normal throughout the summer months with localized outbreaks. During the last two weeks of August, 2009 H1N1 influenza activity again began to increase United States.
In August 2009, CDC reported an additional two instances of oseltamivir-resistant virus infection in two immunosuppressed patients in Seattle, Washington. Later, in mid-September, CDC reported two additional cases of oseltamivir-resistant 2009 H1N1 influenza in two summer campers in North Carolina. CDC and partners continued to carefully track 2009 H1N1 influenza antiviral resistance. As of June 2010 the 2009 H1N1 virus remains susceptible to the antiviral drugs oseltamivir and zanamivir, with rare exception. Cases of antiviral resistance are carefully tracked and updated numbers are posted each week as part of the CDC publication FluView.
In late August, CDC began working with the commercial supply chain (manufacturers, distributors, retailers) for certain influenza countermeasures to monitor national inventory levels of critical supplies (antivirals and respiratory protective equipment) on a weekly basis. This visibility provided important data to guide SNS decision-making leading to the release of additional SNS countermeasures.
FDA and the manufacturer of the antiviral drug TamifluВ® (oseltamivir) recognized that commercial and stockpiled supplies of TamifluВ® oral suspension (liquid formulation meant for children) were limited in October 2009. CDC worked with partners to reach pharmacists with background information, updates on antiviral drug supplies, and instructions on how to compound oral suspension from TamifluВ® capsules meant for adults (Compounding is the mixing of drugs by a health care professional to fit the unique needs of the patient). CDC also provided instructions for parents and caregivers on how to make a medicine mixture for their child using adult TamifluВ® capsules and thick, sweetened liquid. В CDC also analyzed related surveillance data and based on the analysis over 500,000 bottles of pediatric oral suspension were distributed from the CDC SNS to states to fill production gaps and meet the increasing demand for the formulation.
On October 23rd, 2009, FDA issued an Emergency Use Authorization (EUA) for Peramivir IV. Peramivir IV is an investigational intravenous antiviral drug used to treat people who have been hospitalized due to severe flu illness. This drug was held in the Strategic National Stockpile (SNS) and distributed by CDC under an EUA. Licensed clinicians were able to request this product through the CDC website electronic request system, and product was delivered directly to hospital facilities. Also in October, HHS authorized the release of an additional 59.5 million N95 respirators.
CDC closed out reports of 2009 H1N1 hospitalizations and deaths for the 2008-09 season in late August. On August 30, 2009, reporting modifications were implemented to allow states to report hospitalizations and deaths associated with any influenza or to report hospitalizations and deaths using a pneumonia and influenza syndromic case definition through the Aggregate Hospitalizations and Deaths Reporting Activity (AHDRA). This change in reporting was implemented in order to provide a fuller picture of the burden of serious flu illness and deaths during the pandemic. The new reporting season for the 2009-2010 flu season began on August 30, 2009, and the first new numbers for the 2009-2010 season were reported in the September 11, 2009 issue of FluView.
Over the course of the pandemic, CDC refined and revised its surveillance methods, eventually developing a methodology based on surveillance data to estimate the range of 2009 H1N1 cases, hospitalizations and deaths in the United States. CDC released its first official estimates for 2009 H1N1 cases, hospitalizations and deaths on November 12, 2009, and updated these on December 10, 2009, January 15, 2010, February 12, 2010, March 12, 2010, April 19, 2010 and for the final time on May 14, 2010.
2009 H1N1 Vaccination
The emergence and spread of the 2009 H1N1 virus resulted in extraordinary influenza-like illness activity in the United States throughout the summer and fall months of 2009. During this period, influenza activity reached its highest level in the reporting week ending October 24, 2009, with 49 of 50 states reporting geographically widespread disease. A cornerstone of the U.S. Government response to the 2009 H1N1 pandemic was the launch of the national influenza 2009 H1N1 vaccination campaign that began in October.
Much activity led up to the launch of the vaccination campaign.
Starting in early June 2009, weekly calls were held to provide state and local planners with vaccine-related updates, and on July 8, 2009, CDC issued guidance for state and local public health departments to assist them in planning for the 2009 H1N1 influenza vaccination campaign. On July 9, 2009, the Department of Health and Human Services, the Department of Homeland Security, the Department of Education, and the White House held an influenza preparedness summit for federal, state, local and tribal officials to discuss existing pandemic plans, lessons learned, and preparedness priorities. At the summit, the Federal government announced the availability of $350 million in supplemental funding for use by state, local and territorial health departments to bolster their response activities to the 2009 H1N1 influenza pandemic and strongly encouraged state, tribal and local partners to be ready to begin a 2009 H1N1 influenza immunization program by mid-October 2009.
The 2009 National Influenza Vaccine Summit, a partnership of public and private stakeholders committed to achieving the Healthy People 2010 goals for influenza vaccine, convened on June 29. During the 2009 Summit, attendees were provided updates by experts in several professional fields, including private medicine, public health, health communication, vaccine manufacturing, vaccine distribution, and vaccine-related policy.В CDC has been a cosponsor of this event, along with the American Medical Association, since 2001.
In preparation for the 2009 H1N1 influenza immunization program, on July 22, 2009, В the National Institutes of Health (NIH) announced the start of a series of clinical trials to test pilot lots of two manufacturersвЂ™ versions of 2009 H1N1 influenza vaccine in healthy people, as well as people with underlying health conditions like asthma and HIV. Preliminary results from the clinical trials were announced publicly.
On July 23, 2009, FDAвЂ™s Vaccines and Related Biological Advisory Committee indicated support of FDAвЂ™s proposed plan to license monovalent 2009 H1N1 vaccines via a вЂњstrain changeвЂќ pathway, similar to how seasonal influenza vaccines are licensed. This meant the 2009 H1N1 vaccine would be made in the same way using the same standards already in place for seasonal vaccines; it also allowed licensure to proceed more quickly since it did not require immunogenicity data or additional safety (except for the live attenuated vaccine) data for licensure.
On July 29, 2009, the Advisory Committee for Immunization Practices (ACIP) met to make recommendations for 2009 H1N1 vaccine. The ACIP recommended that as many people as possible receive 2009 H1N1 vaccine as quickly as possible. Certain groups of people were targeted to receive initially limited supplies of the 2009 H1N1 vaccine based on epidemiologic and virologic data indicating they were at higher risk for infection or for severe influenza complications. The initial target groups for vaccination were estimated to consist of about 159 million people and included: pregnant women, people who live with or care for infants younger than 6 months of age, health care and emergency medical services personnel, infants 6 months through young adults 24 years of age, and adults 25 through 64 years of age who are at higher risk for 2009 H1N1 complications because of chronic health disorders or compromised immune systems. The ACIP also recommended that local public health authorities and health care practitioners have flexibility to determine at the local level how quickly and when to expand vaccination to other groups because vaccine availability and demand would likely vary by area.
CDC convened three public engagement sessions in mid-August in ten regions of the United States with the purpose of soliciting citizen input into vaccination planning. The public provided opinions to CDC regarding how vaccine should be provided in the U.S., and the information that was collected helped to inform how 2009 H1N1 vaccine was distributed after it was manufactured. Ultimately, it was decided that vaccine should be distributed as soon as it was ready so that people could be protected against influenza as soon as possible, versus waiting to distribute vaccine until large quantities were prepared.
In late August, CDC published a study in the MMWR that summarized an investigation of laboratory-confirmed cases of 2009 H1N1 influenza identified during April 24-July 25, 2009 in Chicago, Illinois. The study found that the overall attack rate was highest among children aged 5-14 years (147 per 100,000 population), which was 14 times higher than for adults older than 60 years of age. A total of 205 (13%) patients were hospitalized, with the highest rate observed among children aged 0-4 years (25 per 100,000), followed by children aged 5-14 years (11 per 100,000). These findings would also provide input into vaccination strategy.
By the end of August 2009, prototype vaccines to prevent 2009 H1N1 virus had been developed but were not yet licensed. Production of the enormous quantities of vaccine necessary to protect the entire U.S. population was underway. CDC expanded its contract for the childhood Vaccine for Children program in the United States (McKesson Specialty Distribution), to provide centralized distribution of 2009 H1N1 vaccine. Available vaccine supplies were allocated to states proportional to their total populations and shipped to public and private provider vaccination sites based on orders placed by the states. Participating providers were asked to sign a Provider Agreement assuring they intended to meet state requirements for administering vaccine.
On September 3, 2009, CDC published in the MMWR a study that had analyzed data related to 2009 H1N1 influenza pediatric deaths reported to CDC from April to August, 2009. Data showed that as of August 8, 2009, 477 deaths with laboratory confirmed 2009 H1N1 flu in the United States had been reported to CDC, including 36 children younger than 18 years of age. Sixty-seven percent (67%) of children who died with 2009 H1N1 influenza had at least one high-risk medical condition. CDC continued to urge parents to recognize 2009 H1N1 in their children early and to seek medical attention when needed. CDC also reiterated that all children 6 months or older and caregivers of children younger than 6 months should receive the 2009 H1N1 vaccine when it became available.
On September 10, 2009, the HHS Secretary and CDC Director joined the National Foundation for Infectious Diseases (NFID) in a news conference to stress vigilance against seasonal influenza in an unusual season and urged Americans to get their seasonal flu vaccine early. In addition to NFID, HHS and CDC, the news conference was held in collaboration with the American Medical Association (AMA), American Academy of Pediatrics (AAP), American College of Physicians (ACP), AARP, and the National Influenza Vaccine Summit.
On September 15, 2009, the Food and Drug Administration (FDA) announced its approval of four 2009 H1N1 influenza vaccines, and later, on November 16, FDA announced its approval of a fifth 2009 H1N1 vaccine to protect against the 2009 H1N1 flu virus.
The NIH announced on September 21, 2009, that early results from clinical trials of 2009 H1N1 influenza vaccine in children looked promising. Preliminary analysis indicated that the vaccines were safe, and that only one dose of 2009 H1N1 vaccine for the majority of 10 to 17 year olds would be needed to generate a sufficient immune response to be protective against 2009 H1N1 influenza virus, but younger children generally had a less robust early response to the vaccine. CDC recommended that children younger than 10 years receive two doses of 2009 H1N1 influenza vaccine. Results of trials conducted among adults were later published in December, and the data indicated that the immune response among vaccinated adults was excellent. The safety data from these trials also indicated that vaccine side effects were similar to those seen with the seasonal flu vaccines.
On September 30, 2009, states were able to place their first orders for the 2009 H1N1 vaccine; forty-seven states placed orders on that day, and by October 9, 2009, all states and the District of Columbia had placed orders for vaccine. The first doses were administered on October 5, 2009.
Because initial supplies of vaccine were limited, most state and local health departments requested that vaccine be given only to those in the initial target groups, and many restricted use to those in sub prioritization groups that had also been outlined by ACIP. The first six weeks after vaccines were initially released where characterized by high demand for vaccine and limited availability. On October 23, the ACIP discussed pandemic vaccine issues, including suitability of the initial target groups developed in July 2009, and concluded that the July guidance remained appropriate. The ACIP continued to emphasize the role of local decision-making in determining when to begin offering vaccine to persons outside initial target groups.
As vaccine supply increased, by late November and early December most states had begun easing restrictions for 2009 H1N1 vaccine use, and by late December vaccination had been opened up to anyone who wanted it. Also beginning in December 2009, the HHS Center for Faith-Based Neighborhood Partnerships partnered with the HHS Regional Offices to host eleven teleconferences to engage community and faith-based organizations in the 2009 H1N1 flu response. Since most states were easing vaccination restrictions, these calls presented an opportunity to remind key partners that they should check with their local health departments to determine availability of vaccine. By the week of December 22, distribution of 2009 H1N1 vaccine had been opened up to retail pharmacies so that they could place orders for vaccine directly, thereby expanding the reach and availability of vaccine.
In December 2009, CDC published in the MMWR preliminary safety results for the 2009 H1N1 vaccines from the first months of reports received through the U.S. Vaccine Adverse Event Reporting System (VAERS), a national voluntary reporting surveillance system and data from the Vaccine Safety Datalink. Results indicated that the vast majority (95%) of adverse events reported to VAERS after receipt of the 2009 H1N1 vaccine were not serious (e.g., soreness at the vaccine injection site). Of the 3,783 reports, 204 (5%) were reports that involved what would be coded as serious health events (defined as life threatening or resulting in death, major disability, abnormal conditions at birth, hospitalization, or extension of an existing hospitalization). The percentage of reports involving what would be considered serious health events was not substantially different between 2009 H1N1 and seasonal influenza vaccines.
The 2009 H1N1 influenza vaccine was manufactured in several formulations, using the same manufacturers and the same manufacturing practices used to produce seasonal influenza vaccine. Monitoring the safety of the flu vaccine continues to be a top priority. CDC and the Food and Drug Administration (FDA) worked with other agencies to establish and enhance existing surveillance systems to rapidly detect any unexpected adverse events among persons who are vaccinated and to adjust the vaccination program, if necessary, to minimize risks and maximize benefits from vaccination. Two important systems used to monitor vaccine safety that have been active for 20 years, are the Vaccine Adverse Events Reporting System (VAERS), jointly operated between CDC and FDA, and the Vaccine Safety Datalink (VSD) , a collaborative project between the CDC and eight managed care organizations covering more than nine million members(about 3% of the US population). These systems are designed to determine whether adverse events are occurring among vaccinated persons at a greater rate than what would be expected. CDC worked with FDA and other partners to strengthen these vaccine safety monitoring systems and develop new ways to monitor vaccine safety. In addition, based on the recommendation of the National Vaccine Advisory Committee (NVAC), HHS established the H1N1 Vaccine Safety Risk Assessment Working Group to review 2009 H1N1 vaccine safety data as it accumulates. This working group of outside experts conducts regular, rapid reviews of available data from the federal safety monitoring systems and presents them to NVAC and federal leadership for appropriate policy action and follow-up.
Also in December 2009, HHS joined with the Ad Council to launch a new nationwide Public Service Announcements campaign called Together We Can Fight the Flu that encouraged Americans to get vaccinated against the 2009 H1N1 virus. The week of December 18, 2009 marked the first 100 million doses of 2009 H1N1 vaccine available for ordering.
The year 2010 began with the National Influenza Vaccination Week (NIVW). NIVW is a national observance that was established to highlight the importance of continuing influenza vaccination after the holiday season into January and beyond. The President of the United States proclaimed the week of January 10-16, 2010, National Influenza Vaccination Week, and encouraged all Americans to observe the week by getting the 2009 H1N1 flu vaccine and by asking their families, friends and coworkers to do the same. CDC and HHS — in conjunction with the states and many other partners, both public and private — launched a comprehensive NIVW campaign with the objective of raising vaccination awareness, providing educational opportunities, free resources, as well as vaccination clinics. Every year, certain days during NIVW are designated to highlight the importance for certain groups; this yearвЂ™s Week was dedicated to highlighting the importance of vaccination for the general public and health care workers, people with chronic health conditions that put them at high risk of serious influenza-related complications, children, pregnant women, and caregivers of infants less than 6 months old, young adults 19 through 24 years old, and people 65 years and older. For example, the events on Tuesday, January 12 centered on people with chronic medical conditions that put them at higher risk of serious influenza-related complications. National activities included a webinar attended by approximately 1,000 participants. This joint effort was hosted by HHS, CDC, the American Cancer Society, the American Diabetes Association, and the American Lung Association. In addition, Secretary Sebelius participated in two press conference calls announcing new public service announcements (PSAs) tailored to African American and Native American audiences. The Director of the Indian Health Service joined the Secretary in stressing the importance and benefits of vaccination.
On January 15, 2010, CDC published an article in the MMWR on influenza A (H1N1) 2009 monovalent vaccination coverage in the United States between October and December 2009. Results of the study indicated that efforts to get available vaccine to target groups had largely succeeded. Early on during the 3-month period, 85% of available vaccine reached people within those initial target populations. By the end of December, with many programs expanding their vaccine efforts to all populations, 74% of all vaccine given during the program had gone to people in the initial priority groups.
On February 18, 2010, the World Health Organization (WHO) published recommendations for the composition of influenza virus vaccines for the upcoming season in the Northern Hemisphere (November 2010-April 2011). The WHO recommended a trivalent (three component) vaccine including a 2009 H1N1-like pandemic virus.В In February of 2010, the components of the 2010-2011 influenza vaccine were announced. The 2010-2011 flu vaccine will protect against a 2009 H1N1-like virus in addition to an influenza A H3N2 virus and an influenza B virus.
The United States experienced its second wave of 2009 H1N1 activity in the fall with activity peaking during the second week in October. After that, activity declined quickly to below baseline levels in January, but persisted for several more months at lower levels. However, by May, influenza activity levels in the United States were low across key flu indicators. Reporting for the 2009-2010 influenza season was finalized on May 28, 2010. Even as flu activity reached normal summer-time levels in the U.S., CDC continued to recommend influenza vaccination, particularly for high risk persons, because of reports of ongoing sporadic cases of 2009 H1N1, ongoing spread of 2009 H1N1 in the Southern Hemisphere and the possibility that 2009 H1N1 viruses might circulate early during the upcoming flu season.
CDC Communication Activities During the 2009 H1N1 Pandemic
The CDC response to the 2009 H1N1 pandemic was led by science and continually evolved to meet the nationвЂ™s needs as events unfolded and as more information became available. However, a consistent underlying communications strategy underscored the entire CDC response. The strategy is based on the emergency risk communications principles of quickly, proactively and transparently communicating accurate information to the public and to partners. This strategy included CDC clearly stating its goals and actions in response to the evolving situation and acknowledging what was not known, as well as what was known. Another important part of the strategy was CDC setting the expectation that information and advice would change rapidly as the situation evolved. From the earliest days of the pandemic, CDC regularly articulated its goals to вЂњreduce transmission and illness severity, and provide information to help health care providers, public health officials and the public address the challenges posed by the new virus.вЂќ Throughout the response, in an effort to provide the most helpful information in the most effective ways possible, CDC drew on existing knowledge but also worked with partners to conduct ongoing scientific research and evaluation of peopleвЂ™s knowledge, attitudes and practices related to a number of topics including 2009 H1N1 flu, infection control guidance, and vaccine.
Especially during the early days of the outbreak, the release of information from CDC and exchange of information with partners was conducted on a 24-hour cycle. This included frequent updates to media and the public, the consistent use of a core group of spokespersons, daily information outreach to partners, and rapid establishment and ongoing maintenance of an extensive Web site dedicated specifically to the emergency response for 2009 H1N1 flu. The goal was not only to be as transparent as possible in all activities related to managing the public health response, but also to maintain credibility and continue to be a trusted source of information for the public and for partners.
Beginning early in the response and continuing throughout the year and into 2010, special care was taken to keep state and local public health partners informed of CDCвЂ™s activities. Key messages were regularly provided to help maintain consistent, clear communication across the response. Special care also was taken to regularly collect feedback from state and local public health partners to help ensure that CDC recommendations were finely tuned to what was happening in the field. Regularly scheduled conference calls with the Association of State and Territorial Health Officials, the National Association of City and County Health Officials, and the National Public Health Information Coalition proved to be an effective way to share information. In addition, on April 24, 2009, CDC held the first of more than 30 Clinician Outreach and Communication Activity (COCA) calls presented on a variety of 2009 H1N1-related topics. COCA is designed to reach a diverse group of health care providers and provide a system through which clinicians can communicate their educational needs to CDC and receive answers to questions about related emerging diseases. At the peak of the 2009 H1N1 response, COCA had more than 41,100 listserv subscribers.
CDC also worked hard to keep the policy community informed.В CDC provided responses to congressional requests for information and briefings on 2009 H1N1-related issues, and also provided email and web-based informational updates as the pandemic unfolded.В In all, CDC participated in 14 hearings, provided technical assistance in another 12 hearings, issued over three dozen 2009 H1N1 newsletters to policymakers, arranged for over 40 congressional briefings or speaking engagements and fielded over 350 congressional inquiries during the pandemic.
There was a concerted effort to get information out as soon as possible and to keep the public and partners aware of developments as they unfolded, even as guidance was changing quickly. For example, when relatively few cases of human infection with this virus were lab confirmed and severity of the pandemic was not known, on April 28, 2009, CDC posted guidance for schools and advised that they close if they had a suspected or actual case of the flu in order to lessen the risk of spreading 2009 H1N1 into their communities. As more information became available suggesting a lower risk of severe illness and death from 2009 H1N1, six days later the recommendation was changed to recommend against school closure for community mitigation purposes.
The development of CDC guidance is an example of the collaborative communication and sharing of information that took place between CDC, HHS, other federal agencies, and external partners. Development of appropriate guidance often relied on CDC communication with many external partners several times a week, with the goal of achieving consensus on what the best practice would be given the best science currently available. For example, CDC worked with representatives from a number of organizations including but not limited to Council of State and Territorial Epidemiologists (CSTE), National Association of County and City Health Officials (NAACHO), American Academy of Pediatrics (AAP), American Academy of Family Physicians (AAFP), American College of Obstetricians and Gynecologists (ACOG), Association of State and Territorial Health Officials (ASTHO), American College of Physicians (ACP), Infectious Diseases Society of America (ISDA), American Academy of Pediatrics (AAP), Food and Drug Administration (FDA) and World Health Organization (WHO), during the development of guidance related to everything from surveillance systems to the appropriate use of antiviral drugs during the pandemic. On the topic of vaccination, these discussions helped inform decision-making by the Advisory Committee on Immunization Practices (ACIP).
Apart from ongoing collaboration between CDC and its external partners, the communications response for 2009 H1N1 flu also was characterized by ongoing, close coordination between CDCвЂ™s communicators and its scientists to ensure that messages stayed scientifically accurate. Also, CDC communicators took time to regularly analyze feedback from a variety of external sources, including polls and surveys, in order to ensure that CDC’s messages were clear.
CDC provided a steady stream of information to audiences across the spectrum: from the public to pharmacists to laboratorians to international partners and countries around the globe. Information provided by CDC reached a myriad of audiences through a variety of channels including but not limited to: a 24-hour information hotline, press briefings for the media, dissemination through health alert networks, daily postings (including video and audio podcasts) to the CDC 2009 H1N1 web site, regular updates on Facebook and Twitter, and further outreach by partners and partner organizations to their own audiences, just to name a few channels.В For example, in November 2009, CDC kicked off a national travelersвЂ™ health public awareness campaign and urged travelers to plan ahead and stay informed about what to do if they got sick while they were away from home. The campaign used a variety of media, including informational posters distributed at over 300 ports of entry in the United States, national radio and print advertising, and social media and online outreach, which culminated in over 80 million exposures.В CDC also coordinated with HHS and the Flu.gov web site and posted communication toolkits for the 2009-2010 influenza season for businesses, employers, childcare groups and institutions of higher education.
The CDC 2009 H1N1 influenza and seasonal influenza vaccination campaign was made up of multiple outreach efforts including placement of articles geared to numerous audiences like parents and young adults, in high-profile media outlets. Article placements led to nearly 403 million overall impressions. Other national outreach efforts made via social media tools, radio ads, two television public service announcements (PSAs), online media banners, and city bus ads. Numerous print materials in multiple languages were made for partners to distribute and were downloaded tens of thousands of times. Special audiences identified for additional print materials included Native Americans, African Americans, Hispanics, pregnant women, young adults, first responders, and health care workers.
In addition to materials provided for the 2009 H1N1 and seasonal influenza vaccination campaign, CDC provided other key materials in multiple languages. For example, the entire English-language 2009 H1N1 web site was mirrored in Spanish. In addition, key tools and resources were created in Chinese, Vietnamese, Korean, French, German, Arabic, Russian, Amharic, Farsi, Somali, Karen, Burmese, Cambodian, and Kirundi.В
In all, between April 2009 when 2009 H1N1 flu first emerged and April 2010, CDC held 60 related media events вЂ“ 39 press briefings and 22 telebriefings вЂ“ for a total of more than 35,000 participants. CDC also hosted its first ever two-day workshop for the news media on the subjects of both 2009 H1N1 influenza and seasonal influenza in late August. Originally conceived to include 12 members of the news media, the attendance grew to over 40 journalists from national, regional and local news outlets representing radio, television, newspapers, magazines, and online news media. Speakers at the event included the Secretary of Health and Human Services, the CDC Director, influenza experts, vaccine safety experts, and laboratory experts.В В The CDC hotline (1-800-CDC-INFO) responded to more than 211,000 related inquiries from the general public and health care providers, and the CDC 2009 H1N1 web site had more than 219,595,000 page views. Also, the number of CDC Facebook fans rose to more than 55,000 fans and the CDC emergency profile on Twitter was tracked by more than 1,200,000 followers.
Swine Flu (H1N1)
Swine flu, also known as the H1N1 virus, is a relatively new strain of an influenza virus that causes symptoms similar to the regular flu. It originated in pigs but is spread primarily from person to person.
Swine flu made headlines in 2009 when it was first discovered in humans and became a pandemic. Pandemics are contagious diseases affecting people throughout the world or on multiple continents at the same time.
The World Health Organization (WHO) declared the H1N1 pandemic over in August 2010. Since then, the H1N1 virus has been known as a regular human flu virus. It continues to spread during flu season like other strains of the flu. The flu shot developed each year by the Centers for Disease Control and Prevention (CDC) usually includes a vaccination against a type of H1N1 virus.
Like other strains of the flu, H1N1 is highly contagious, allowing it to spread quickly from person to person. A simple sneeze can cause thousands of germs to spread through the air. The virus can linger on tables and surface areas like door knobs, waiting to be picked up.
The best means of dealing with swine flu is to prevent it. Hand sanitization is important to stop the spread of the virus. Staying away from infected people will help stop person-to-person transmission.
When it first emerged, swine flu was most common in children 5 years and older and young adults. This was unusual because most flu virus infections are a higher risk for complications in older adults or the very young. Today, risk factors for getting swine flu are the same as for any other strain of the flu. You’re most at risk if you spend time in an area with a large number of people who are infected with swine flu.
Some people are at higher risk for becoming seriously ill if they’re infected with swine flu. These groups include:
- adults over age 65
- children under 5 years old
- young adults and children under age 19 who are receiving long-term aspirin (Bufferin) therapy
- people with compromised immune systems (due to a disease such as A >
Swine flu is caused by a strain of influenza virus that usually only infects pigs. Unlike typhus, which can be transmitted by lice or ticks, transmission usually occurs from person to person, not animal to person.
You can’t catch swine flu from eating properly cooked pork products.
Swine flu is very contagious. The disease is spread through saliva and mucus particles. People may spread it by:
Swine Flu (Swine Influenza A [H1N1 and H3N2])
Swine flu (H1N1 and H3N2 influenza virus) facts
- Swine flu is a respiratory disease caused by influenzaviruses that infect the respiratory tract of pigs and result in a barking cough, decreased appetite, nasal secretions, and listless behavior; the virus can be transmitted to humans.
- Swine flu viruses may mutate (change) so that they are easily transmissible among humans.
- The April 2009 swine flu outbreak (pandemic) was due to infection with the H1N1 virus and was first observed in Mexico.
- Symptoms of swine flu in humans are similar to most influenza infections: fever (100 F or greater), cough, nasal secretions, fatigue, and headache.
- The incubation period for the disease is about one to four days.
- Swine flu is contagious about one day before symptoms develop to about five to seven days after symptoms develop; some patients may be contagious for a longer time span.
- The disease lasts about three to seven days with more serious infections lasting about nine to 10 days.
- Vaccination is the best way to prevent or reduce the chances of becoming infected with influenza viruses.
- Primary care specialists, pediatricians, and emergency-medicine doctors usually treat the disease, but other specialists may be consulted if the flu is severe, complicated, and/or life threatening.
- Four antiviral agents, zanamivir (Relenza), oseltamivir (Tamiflu), peramivir (Rapivab), and baloxavir marboxil (Xofluza), have been reported to help prevent or reduce the effects of swine flu if taken within 48 hours of the onset of symptoms. Some researchers disagree and suggest the antiviral agents have no effect.
- There are various methods listed in this article to help indiv >
What is the swine flu?
Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs, resulting in nasal secretions, a barking cough, decreased appetite, and listless behavior. Swine flu produces most of the same symptoms in pigs as human flu produces in people. Swine flu can last about one to two weeks in pigs that survive. Swine influenza virus was first isolated from pigs in 1930 in the U.S. and has been recognized by pork producers and veterinarians to cause infections in pigs worldwide. In a number of instances, people have developed the swine flu infection when they are closely associated with pigs (for example, farmers, pork processors), and likewise, pig populations have occasionally been infected with the human flu infection. In most instances, the cross-species infections (swine-origin virus to man; human flu virus to pigs) have remained in local areas and have not caused national or worldwide infections in either pigs or humans. Unfortunately, this cross-species situation with influenza viruses (human infections with swine viruses) has had the potential to change. Investigators decided the 2009 so-called «swine flu» strain, first seen in Mexico, should be termed novel H1N1 flu since it was mainly found infecting people and exhibits two main surface antigens, H1 (hemagglutinin type 1) and N1 (neuraminidase type1). The eight RNA strands from novel H1N1 flu have one strand derived from human flu strains, two from avian (bird) strains, and five from swine strains.
The main swine flu viruses in pigs in the recent years are swine triple reassortant (tr; it means a viral strain with genes from three different organisms) H1N1, trH3N2, and trH1N2. However, in August 2020, China first reported a new swine flu outbreak in pigs in Liaoning province. The pig flu strain known as African swine flu (although some researchers think it originated in Russia), almost 100% fatal to pigs, was the cause. This strain is highly infectious, survives in heat and cold environments, and can remain viable and infectious on surfaces for days to weeks. Currently, there is no effective vaccine or drug to stop its spread, so the disease is treated by immediate slaughter of infected pigs. China has about 50% of the world’s pig population and relies on pork to prov >
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What to Do if You Think You Have H1N1 Swine Flu Virus
If you’ve got fever, cough, or one of the other symptoms of the flu, you may be wondering if you have contracted the H1N1 swine flu virus. The reality is that it isn’t possible to know unless specialized testing is ordered, and for uncomplicated cases of the flu in non-hospitalized patients, routine testing for the H1N1 virus is not being carried out.
How is swine flu transmitted? Is swine flu contagious?
Swine influenza is transmitted from person to person by inhalation or ingestion of droplets containing virus from people sneezing or coughing; it is not transmitted by eating cooked pork products. The newest swine flu virus that has caused swine flu is influenza A H3N2v (commonly termed H3N2v) that began as an outbreak in 2011. The «v» in the name means the virus is a variant that normally infects only pigs but has begun to infect humans. There have been small outbreaks of H1N1 influenza since the pandemic; a recent one is in India where at least three people have died.
What is the incubation period for swine flu?
The incubation period for swine flu is about one to four days, with the average being two days; in some people, the incubation period may be as long as about seven days in adults and children.
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What is the contagious period for swine flu?
The contagious period (human-to-human viral infection) for swine influenza in adults usually begins one day before symptoms develop in an adult and it lasts about five to seven days after the person becomes sick. However, people with weakened immune systems and children may be contagious for a longer period of time (for example, about 10 to 14 days).
How long does the swine flu last?
In uncomplicated infections, swine flu typically begins to resolve after three to seven days, but the malaise and cough can persist two weeks or more in some patients. Severe swine flu may require hospitalization that increases the length of time of infection to about nine to 10 days.
What causes swine flu?
The cause of the 2009 swine flu was an influenza A virus type designated as H1N1. In 2011, a new swine flu virus was detected. The new strain was named influenza A (H3N2)v. Only a few people (mainly children) were first infected, but officials from the U.S. Centers for Disease Control and Prevention (CDC) reported increased numbers of people infected in the 2012-2013 flu season. Currently, there are not large numbers of people infected with H3N2v. Unfortunately, another virus termed H3N2 (note no «v» in its name) has been detected and caused flu, but this strain is different from H3N2v. In general, all of the influenza A viruses have a structure similar to the H1N1 virus; each type has a somewhat different H and/or N structure.
Why is swine flu now infecting humans?
Many researchers now consider that two main series of events can lead to swine flu (and also avian or bird flu) becoming a major cause for influenza illness in humans.
First, the influenza viruses (types A, B, C) are enveloped RNA viruses with a segmented genome; this means the viral RNA genetic code is not a single strand of RNA but exists as eight different RNA segments in the influenza viruses. A human (or bird) influenza virus can infect a pig respiratory cell at the same time as a swine influenza virus; some of the replicating RNA strands from the human virus can get mistakenly enclosed inside the enveloped swine influenza virus. For example, one cell could contain eight swine flu and eight human flu RNA segments. The total number of RNA types in one cell would be 16; four swine and four human flu RNA segments could be incorporated into one particle, making a viable eight RNA-segmented flu virus from the 16 available segment types. Various combinations of RNA segments can result in a new subtype of virus (this process is known as antigenic shift) that may have the ability to preferentially infect humans but still show characteristics unique to the swine influenza virus (see Figure 1). It is even possible to include RNA strands from birds, swine, and human influenza viruses into one virus if a single cell becomes infected with all three types of influenza (for example, two bird flu, three swine flu, and three human flu RNA segments to produce a viable eight-segment new type of flu viral genome). Formation of a new viral type is considered to be antigenic shift; small changes within an individual RNA segment in flu viruses are termed antigenic drift (see figure 1) and result in minor changes in the virus. However, these small genetic changes can accumulate over time to produce enough minor changes that cumulatively alter the virus’ makeup over time (usually years).
Second, pigs can play a unique role as an intermediary host to new flu types because pig respiratory cells can be infected directly with bird, human, and other mammalian flu viruses. Consequently, pig respiratory cells are able to be infected with many types of flu and can function as a «mixing pot» for flu RNA segments (see figure 1). Bird flu viruses, which usually infect the gastrointestinal cells of many bird species, are shed in bird feces. Pigs can pick these viruses up from the environment, and this seems to be the major way that bird flu virus RNA segments enter the mammalian flu virus population. Figure 1 shows this process in H1N1, but the figure represents the genetic process for all flu viruses, including human, swine, and avian strains like H1N2 (bird flu).
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What are swine flu symptoms and signs?
Symptoms of swine flu are similar to most influenza infections: fever (100 F or greater), cough (usually dry), nasal secretions, fatigue, and headache, with fatigue being reported in most infected individuals. Some patients may also get a sore throat, rash, body (muscle) aches or pains, headaches, chills, nausea, vomiting, and diarrhea. In Mexico, many of the initial patients infected with H1N1 influenza were young adults, which made some investigators speculate that a strong immune response, as seen in young people, may cause some collateral tissue damage. The incubation period from exposure to first symptoms is about one to four days, with an average of two days. The symptoms last about one to two weeks and can last longer if the person has a severe infection.
Some patients develop severe respiratory symptoms, such as shortness of breath, and need respiratory support (such as a ventilator to breathe for the patient). Patients can get pneumonia (bacterial secondary infection) if the viral infection persists, and some can develop seizures. Death often occurs from secondary bacterial infection of the lungs; appropriate antibiotics need to be used in these patients. The usual mortality (death) rate for typical influenza A is about 0.1%, while the 1918 «Spanish flu» epidemic had an estimated mortality rate ranging from 2%-20%. Swine (H1N1) flu in Mexico had about 160 deaths and about 2,500 confirmed cases, which would correspond to a mortality rate of about 6%, but these initial data were revised and the mortality rate worldwide was estimated to be much lower. Fortunately, the mortality rate of H1N1 remained low and similar to that of the conventional flu (average conventional flu mortality rate is about 36,000 per year; projected H1N1 flu mortality rate was 90,000 per year in the U.S. as determined by the president’s advisory committee, but it never approached that high number).
Fortunately, although H1N1 developed into a pandemic (worldw >
What types of health care professionals treat swine flu?
Almost all uncomplicated patients with swine flu can be treated at home or by the patient’s pediatrician, primary care prov >
What tests do health care professionals use to diagnose swine flu?
Swine flu is presumptively diagnosed clinically by the patient’s history of association with people known to have the disease and their symptoms listed above. Usually, a quick test (for example, nasopharyngeal swab sample) is done to see if the patient is infected with influenza A or B virus. Most of the tests can distinguish between A and B types. The test can be negative (no flu infection) or positive for type A and B. If the test is positive for type B, the flu is not likely to be swine flu. If it is positive for type A, the person could have a conventional flu strain or swine flu. However, the accuracy of these tests has been challenged, and the U.S. Centers for Disease Control and Prevention (CDC) has not completed their comparative studies of these tests. However, a new test developed by the CDC and a commercial company reportedly can detect H1N1 reliably in about one hour; the test was formerly only available to the military. In 2010, the FDA approved a commercially available test that could detect H1N1 within four hours. Most of these rapid tests are based on PCR technology.
Swine flu is definitively diagnosed by >
What is the treatment for swine flu?
The best treatment for influenza infections in humans is prevention by vaccination. Work by several laboratories has produced vaccines. The first H1N1 vaccine released in early October 2009 was a nasal spray vaccine that was approved for use in healthy individuals ages 2-49. However, the use of nasal spray has not been recommended since 2020. The injectable vaccine, made from killed H1N1, became available in the second week of Oct. 2009. This vaccine was approved for use in ages 6 months to the elderly, including pregnant females. The CDC approved both of these vaccines only after they had conducted clinical trials to prove that the vaccines were safe and effective.
Almost all vaccines have some side effects. Common side effects of H1N1 vaccines (alone or in combination with other flu viral strains) are typical of flu vaccines used over many years and are as follows:
- Flu shot: Soreness, redness, minor swelling at the shot site, muscle aches, low-grade fever, and nausea do not usually last more than about 24 hours.
- Nasal spray: runny nose, low-grade fever, vomiting, headache, wheezing, cough, and sore throat
- Intradermal shot: redness, swelling, pain, headache, muscle aches, fatigue
The flu shot (vaccine) is made from killed virus particles so a person cannot get the flu from a flu shot. However, the nasal spray vaccine contains live virus that have been altered to hinder its ability to replicate in human tissue. People with a suppressed immune system should not get vaccinated with the nasal spray. Also, most vaccines that contain flu viral particles are cultivated in eggs, so individuals with an allergy to eggs were cautioned about getting the vaccine unless tested and advised by their doctor that they are cleared to get it . However, more refined vaccine preparations have contained very few egg allergens, so the egg allergy factor of vaccines has been almost eliminated. Like all vaccines, rare events may occur in some rare cases (for example, swelling, weakness, or shortness of breath). About one person in 1 million who gets the vaccine may develop a neurological problem termed Guillain-Barré syndrome, which can cause weakness or paralysis, difficulty breathing, bladder and/or bowel problems, and other nerve problems. If any symptoms like these develop, see a physician immediately.
Several antiviral agents have been reported to help prevent or reduce the effects of swine flu. The most used are zanamivir (Relenza) and oseltamivir (Tamiflu), both of which are also used to prevent or reduce influenza A and B symptoms. These drugs should not be used indiscriminately, because viral resistance to them can and has occurred. Also, they are not recommended if the flu symptoms already have been present for 48 hours or more, although hospitalized patients may still be treated past the 48-hour guideline. The CDC has suggested in their guidelines that pregnant females can be treated with the two antiviral agents. Severe infections in some patients may require additional supportive measures such as ventilation support and treatment of other infections like pneumonia that can occur in patients with a severe flu infection. Two other new antiviral drugs (Rapivab and Xofluza) may also be used under certain conditions. Some researchers suggest the data on Tamiflu and Relenza is not correct and suggest the antivirals are not effective.
On Dec. 22, 2014, the FDA approved the first new anti-influenza drug (for H1N1 and other influenza virus types) in 15 years, peramivir injection (Rapivab). It is approved for use in the following settings:
Diarrhea, skin infections, hallucinations, and/or altered behavior may occur as side effects of this drug.
- Adult patients for whom therapy with an intravenous (IV) medication is clinically appropriate, based upon one or more of the following reasons:
- The patient is not responding to either oral or inhaled antiviral therapy, or
- drug delivery by a route other than IV is not expected to be dependable or is not feasible, or
- the physician dec >
Another new drug, baloxavir marboxil (Xofluza), is an oral antiviral approved in 2020 for use in children 12 years and older.
What is the history of swine flu in humans?
In 1976, there was an outbreak of swine flu at Fort Dix. This virus was not the same as the 2009 H1N1 outbreak, but it was similar insofar as it was an influenza A virus that had similarities to the swine flu virus. There was one death at Fort Dix. The government decided to produce a vaccine against this virus, but the vaccine was associated with rare instances of neurological complications (Guillain-Barré syndrome) and was discontinued. Some individuals speculate that formalin, used to inactivate the virus, may have played a role in the development of this complication in 1976. One of the reasons it takes a few months to develop a new vaccine is to test the vaccine for safety to avoid the complications seen in the 1976 vaccine. Individuals with active infections or diseases of the nervous system are also not recommended to get flu vaccines.
Early in the spring of 2009, H1N1 flu virus was first detected in Mexico, causing some deaths among a «younger» population. It began increasing during the summer 2009 and rapidly circulated to the U.S. and to Europe and eventually worldwide. The WHO declared it first fit their criteria for an epidemic and then, in June 2009, the WHO declared the first flu pandemic in 41 years. There was a worldwide concern and people began to improve in hand washing and other prevention methods while they awaited vaccine development. The trivalent vaccine made for the 2009-2010 flu season offered virtually no protection from H1N1. New vaccines were developed (both live and killed virus) and started to become available in Sept. 2009-Oct. 2009. The CDC established a protocol guideline for those who should get the vaccine first. By late December to January, a vaccine against H1N1 was available in moderate supply worldwide. The numbers of infected patients began to recede and the pandemic ended. However, a strain of H1N1 was incorporated into the yearly trivalent vaccine for the 2010-2011 flu season because the virus was present in the world populations.
As stated in the first section of this article, a new strain of swine flu, (H3N2)v, was detected in 2011; it has not affected any large numbers of people in the current flu season. However, another antigenically distinct virus with the same H and N components (termed H3N2 (note no «v») has caused flu in humans; viral antigens were incorporated into the 2013-2014 seasonal flu shots and nasal spray vaccines.
In India in 2015-2020, a large outbreak of swine flu killed more than 1,900 people. During 2020, the numbers of infected people and deaths due to swine flu dropped, but now in 2020 there is a marked resurgence of the disease. The new outbreak of swine flu that began in January 2020 has resulted in 22, 186 people being diagnosed with the infection. There have been 1,094-recorded deaths in 8 months, and the spread of the infection shows no signs of slowing. In the first three weeks of August 2020, 342 deaths were due to swine flu. Unfortunately, private hospitals and clinics do not have to report the number of swine flu diagnoses or deaths, so it is possible according to one medical director of a private clinic, that the current statistics represent «possibly just the tip of the iceberg.» In the U.S., the 2020-2020 flu season was termed a high severity season by the CDC because an estimated 80,000 people died of flu and its complications.
What are the risk factors for swine flu?
Vaccination to prevent influenza is particularly important for people who are at increased risk for severe complications from influenza or at higher risk for influenza-related doctor or hospital visits. When vaccine supply is limited, vaccination efforts should focus on delivering vaccination to the following people since these populations have a higher risk for H1N1 and some other viral infections according to the CDC:
- All children 6 months to 4 years (59 months) of age
- All people 50 years of age and older
- Adults and children who have chronic pulmonary (including asthma) or cardiovascular (except isolated hypertension), renal, hepatic, neurological, hematologic, or metabolic disorders (including diabetes mellitus)
- People who have immunosuppression (including immunosuppression caused by medications or by HIV)
- Women who are or will be pregnant during the influenza season
- Children and adolescents (6 months to 18 years of age) who are receiving long-term aspirin therapy and who might be at risk for experiencing Reye syndrome after influenza virus infection
- Res >
Is it possible to prevent swine flu with a vaccine?
The CDC recommends for the 2020-2020 flu season that everyone 6 months old and older should get a flu shot to prevent or reduce the chance of getting the flu. The best way to prevent novel H1N1 swine flu is vaccination. The CDC recommendations that apply to H1N1, H3N2, and other flu viruses are almost identical to those above-mentioned recommendations for patients at risk when vaccine doses are limited and are as follows:
- Are aged 6 months through 4 years (59 months)
- Are aged 50 years and older
- Have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus)
- Are immunosuppressed (including immunosuppression caused by medications or by human immunodeficiency virus)
- Are or will be pregnant during the influenza season
- Are aged 6 months through 18 years and receiving long-term aspirin therapy and who therefore might be at risk for experiencing Reye’s syndrome after influenza virus infection
- Are residents of nursing homes and other chronic care facilities
- Are American Indians/Alaska Natives
- Are morbidly obese (body-mass index is 40 or greater)
- Are health care personnel
- Are household contacts and caregivers of children aged younger than 5 years and adults aged 50 years and older, with particular emphasis on vaccinating contacts of children aged younger than 6 months
- Are household contacts and caregivers of people with medical conditions that put them at higher risk for severe complications from influenza
- As in previous recommendations, all children aged 6 months to 8 years of age who receive a seasonal influenza vaccine for the first time should receive two doses. Children who received only one dose of a seasonal influenza vaccine in the first influenza season should receive two doses rather than one in the following influenza season.
- A newly approved inactivated trivalent vaccine containing 60 mcg of hemagglutinin antigen per influenza vaccine virus strain (Fluzone High-Dose [Sanofi Pasteur]) is an alternative inactivated vaccine for people 65 years of age and older.
The CDC occasionally makes changes and updates its information on vaccines and other recommendations about any current flu pandemics. The CDC states, «for the most accurate health information, visit http://www.cdc.gov or call 1-800-CDC-INFO, 24/7.» Caregivers should check the vaccine package inserts for more detailed information on the vaccines when they become available.
The CDC says that a good way to prevent any flu disease is to avoid exposure to the virus; this is done by frequent hand washing, not touching your hands to your face (especially the nose and mouth), and avoiding any close proximity to or touching any person who may have flu symptoms. Since the virus can remain viable and infectious for about 48 hours on many surfaces, good hygiene and cleaning with soap and water or alcohol-based hand disinfectants are also recommended. Some physicians say face masks may help prevent getting airborne flu viruses (for example, from a cough or sneeze), but others think the better use for masks would be on those people who have symptoms and sneeze or cough.
The use of Tamiflu, Relenza, or other antivirals may help prevent the flu if taken before symptoms develop or reduce symptoms if taken within about 48 hours after symptoms develop. Some investigators say that administration of these drugs is still useful after 48 hours, especially in high-risk patient populations. However, taking these drugs is not routinely recommended for prevention for the healthy population because investigators suggest that as occurs with most drugs, flu strains will develop resistance to these medications. During the H1N1 pandemic, the CDC made further suggestions about the use of these antiviral medications and developed the interim guidelines for use of Tamiflu, Relenza, and recently updated information for new antivirals peramivir (Rapivab) and Xofluza as follows:
- Patients with high-risk factors should discuss flu symptoms and when to use antiviral medications; doctors should provide a prescription for the antiviral drug for the patient to use if the patient is exposed to flu or develops flu-like symptoms without having to go in to see the doctor.
- «Watchful waiting» was added as a response to taking antiviral medications, with the emphasis on the fact that those people who develop fever and have a preexisting health condition should then begin the antiviral medication.
- The antiviral medications are the first-line medicines for treatment of novel H1N1, H3N2, and H3N2v flu, and many viruses are to date susceptible to Tamiflu, Relenza, Rapivab, and Xofluza.
In general, preventive measures to prevent the spread of flu are often undertaken by those people who have symptoms. Symptomatic people should stay at home, avo >
Is it possible to prevent swine flu if the swine flu vaccine (or other flu strain vaccines) is not readily available?
Although vaccination is the best way to prevent the swine flu, there may be times in the future when the swine flu vaccine may not be available. There are no shortages of the trivalent flu vaccine that contains H1N1 antigens. However, during the 2009 H1N1 pandemic, this situation did occur so people wanted to know what they could do to protect themselves. If, in the future, vaccine supplies do not meet demands, there are some things people can do to try and prevent infection. Without vaccination, the best strategy is to not allow any virus type to contact a person’s mucus. Quarantining any virus-infected people is an extreme measure that may work in some instances (for example, China used this method), but even with quarantining, the virus may still spread by people who have minimal or no symptoms.
The next step, that is easier to be implemented by individuals, is for people with the disease to self-quarantine until they become noninfectious (about seven to 10 days after flu symptoms abate). Infected people can wear surgical masks to reduce the amount of droplet spray from coughs and sneezes and throw away contaminated tissues. Unfortunately, these approaches depend on the compliance of many other people, and the likelihood that such methods will be highly successful in preventing flu virus infections, at best, is only fair. Such methods did not stop the 2009 H1N1 pandemic, although they may have some benefit for a few individuals.
Yet there are still some other methods available to individuals. Perhaps the best way for individuals to try to prevent flu virus infection is a combination of methods that are aimed at fulfilling the very basic principle that if the virus doesn’t reach an individual’s mucus membrane cells, infection will be prevented. The methods are as follows:
- Kill or inactivate the virus before it reaches a human cell by using soap and water to clean your hands; washing clothing and taking a shower will do the same for the rest of your body.
- Use an alcohol-based hand sanitizer if soap and water are not readily available, and use sanitizers on objects that many people may touch (for example, doorknobs, computer keyboards, handrails, phones), although some researchers suggest that such sanitizers are generally ineffective.
- Do not touch your mouth, eyes, nose, unless you first do items 1 or 2 above.
- Avoid crowds, parties, and especially people who are coughing and sneezing (most virus-containing droplets do not travel more than 4 feet, so experts suggest 6 feet away is a good distance to stay). If you cannot avoid crowds (or parties), try to remain aware of people around you and use the 6-foot rule with anyone coughing or sneezing. Do not reach for or eat snacks out of canisters or other containers at parties.
- Avoid touching anything within about 6 feet of an uncovered cough/sneeze, because the droplets that contain virus fall and land on anything usually within that range.
- Studies show that individuals who wear surgical or N95 particle masks may prevent inhalation of some H1N1 virus, but the masks may prevent only about 50% of airborne exposures and offer no protection against surface droplets. However, masks on H1N1 infected people can markedly reduce the spread of infected droplets.
These six steps can help prevent individuals from getting H1N1 and other types of infection, but for many people, adherence to them may be difficult at best. However, there are some additional strategies that may also help prevent viral infections in unvaccinated people according to some investigators. Saline nasal washes and gargling with saline (or a commercial product) as a way to reduce or eliminate viral virus from mucus membranes has been suggested. Proponents of these methods base their rationale on the fact that flu viruses usually take about two to three days to proliferate in nasal/throat cells. While nasal washes and gargling may be soothing to some people, there are no studies that indicate H1N1 or other viruses are killed, inactivated, or completely removed by these methods; conversely, there are no data suggesting these methods cannot have any effect on H1N1. However, with long-term nasal washes using Neti pots, sinus infection with other pathogens may be encouraged.
Other investigators and physicians have offered additional methods that may help reduce exposure to H1N1 virus. For example, Dr. Gerberding, a former CDC director, had several suggestions about how to avoid H1N1 infection on an airplane. She suggested the following:
- If a person is next to you or near (within 6 feet) and is coughing/sneezing, ask the flight attendant to offer the person a mask.
- If there are available seats 6 feet or more away from the coughing/sneezing person, ask to change your seat (planes are good means of travel because the air is recirculated through HEPA filters that can capture viruses, but even the filters will not help if people touch areas where droplets have landed; HEPA filters are usually not available in buses, cars, ships, or trains).
- Turn away from the coughing/sneezing person and turn the air vent toward the person to blow the droplets away from yourself.
Variations of her suggestions may be applicable in many different social or work, or travel situations, but there are no data to prove these methods are effective. In addition, common-sense precautions such as not drinking or eating things touched by others, avoiding casual physical contacts (for example, handshakes, social hugs or kisses, public water fountains [these are OK if you touch nothing and lips only touch flowing water], banisters on stairways, and restroom door handles) will limit exposure to H1N1 and other viruses. Again, these common-sense suggestions lack data substantiation.
Many investigators suggest that people stay well hydrated, take vitamins, and get plenty of rest, but these precautions will not prevent H1N1 or other viral infections, although they may help reduce the effects of infection by strengthening the person’s immune system to fight infection. Similarly, current antiviral medications (described in the preceding section) act on H1N1 and other viruses that have already infected cells; they work by preventing or reducing viral particles from aggregating and being released from infected cells. Timing is important; if only a few cells are infected and the antiviral medications are administered quickly (usually before flu symptoms develop or within 48 hours), the viruses are reduced in number (they cannot easily bud out from the cell surface), so few, if any, other respiratory or mucus membrane cells become infected. This can result in either no flu symptoms or, if a larger number of cells were initially infected, less severe symptoms. The overall effect for the person is that the H1N1 or other viral infection was prevented (it was not; the symptoms were prevented from developing) or that symptoms were reduced.
In the strictest sense of the word prevention, even effective vaccines do not «prevent» infections. What they do accomplish is to alert the immune system to be on guard for certain antigens that are associated with a specific disease-causing agent (for example, H1N1 virus, pneumococcal bacteria). When the agent first infects the host, its antigens are recognized, and these cause a rapid immune response to occur that prevents the pathogen from spreading and developing symptoms in the host. People, including physicians and researchers, often term this complex response to vaccination as «prevention of infection,» but what actually occurs is the prevention of further infection so well that symptoms do not develop or are minimal in the host.
In summary, if H1N1 or other viruses fail to contact cells they can infect, the disease will be prevented. As stated above, this is difficult, but not impossible, to do in almost all societies. Prevention of flu symptoms of infection is possible with antiviral medications if these are given very early in the infection. There are many other methods that may reduce the chance of getting the virus on a person’s mucosal surface, but most methods have not been backed up with objective data. Most doctors and investigators suggest that items that help boost or allow the immune response to function well will help people resist H1N1 and other viral infections and reduce symptoms, but these also do not prevent infections. Consequently, while waiting for a specific antiviral vaccine to be developed or become available, there are some ways indiv >
Are there home remedies for swine flu?
There are many flu «cures» and «treatments» described on the Internet (for example, how cayenne pepper, menthol, or ginseng can be used to treat the flu); before using any of these substances, check with a doctor. However, there are many over-the-counter medications, such as naproxen (Aleve), ibuprofen (Advil and others) and acetaminophen (Tylenol), to reduce fever and discomfort, lozenges to sooth a sore throat, and decongestants to help manage mucus production and coughing. These medications help manage flu symptoms but do not cure the viral disease.
Was swine flu (H1N1) a cause of an epidemic or pandemic in the 2009-2010 flu season?
Yes. An epidemic is defined as an outbreak of a contagious disease that is rapid and widespread, affecting many individuals at the same time. The swine flu outbreak in Mexico fit this definition. A pandemic is an epidemic that becomes so widespread that it affects a region, continent, or the world. On June 11, 2009, WHO officials determined that H1N1 2009 influenza A swine flu reached WHO level 6 criteria (person-to-person transmission in two separate WHO-determined world regions) and declared a swine flu pandemic, the first flu pandemic in 41 years. The H1N1 flu reached over 200 different countries on every continent except Antarctica in the 2009-2010 flu season; fortunately, the severity of the disease did not increase. The following is the CDC data for mortality and morbidity of the 2009 epidemic in the US: final estimates were published in 2011 and state that from Apr. 12, 2009, to Apr. 10, 2010 approximately 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (195,086-402,719), and 12,469 deaths (8868-18,306) occurred in the United States due to H1N1. An outbreak in India that became widespread in that country lasted until late 2020. However, in 2020 another outbreak occurred.
What is the prognosis (outlook) and complications for patients who get swine flu?
In general, the majority (about 90%-95%) of people who get the disease feel terrible (see symptoms) but recover with no problems, as seen in patients in Mexico, the U.S., and many other countries.
People with suppressed immune systems historically have worse outcomes than uncompromised indiv >
Where can I find more information about swine flu (H1N1 and H3N2v)?
For additional information see the following:
«Pregnant Women & Influenza (Flu),» CDC
«Influenza A (H3N2) Variant Virus,» CDC
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United States. Centers for Disease Control and Prevention. «Frequently Asked Flu Questions 2020-2020 Influenza Season.» Updated: Apr 11, 2020.
United States. Centers for Disease Control and Prevention. «Influenza (Flu).» Aug. 8, 2020. .
United States. Centers for Disease Control and Prevention. «Summary of the 2020-2020 Influenza Season.» Nov. 2, 2020. .
United States. Centers for Disease Control and Prevention. «What You Should Know About Flu Antiviral Drugs.» Jan. 5, 2020. .
United States. Centers for Disease Control and Prevention. «Influenza (Flu): Weekly U.S. Influenza Surveillance Report.» Mar. 18, 2020. .
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Treatment of nausea and vomiting depends upon the cause.
H1N1 Flu (Swine Flu)
Swine flu is an infection caused by a virus. It’s named for a virus that pigs can get. People do not normally get swine flu, but human infections can and do happen. In 2009 a strain of swine flu called H1N1 infected many people around the world.
The virus is contagious and can spread from human to human. Symptoms of swine flu in people are similar to the symptoms of regular human flu and include fever, cough, sore throat, body aches, headache, chills and fatigue.
There are antiviral medicines you can take to prevent or treat swine flu. There is a vaccine available to protect against swine flu. You can help prevent the spread of germs that cause respiratory illnesses like influenza by
- Covering your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
- Washing your hands often with soap and water, especially after you cough or sneeze. You can also use alcohol-based hand cleaners.
- Avoiding touching your eyes, nose or mouth. Germs spread this way.
- Trying to avoid close contact with sick people.
- Staying home from work or school if you are sick.
H1N1 (swine flu)
Swine flu is a respiratory disease that normally only infects pigs. Humans who have been in contact with pigs can on rare occasion be infected with it.
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Swine flu (H1N1)
«Swine flu» was the popular name for the virus which was responsible for a global flu outbreak (called a pandemic) in 2009 to 2010. It’s a type of seasonal flu and is now included in the annual flu vaccine.
The scientific name for swine flu is A/H1N1pdm09. It’s often shortened to «H1N1».
«Swine flu» pandemic 2009 to 2010
The virus was first identified in Mexico in April 2009. It became known as swine flu because it’s similar to flu viruses that affect pigs.
It spread rapidly from country to country because it was a new type of flu virus that few young people were immune to.
Overall, the outbreak was not as serious as originally predicted, largely because many older people were already immune to it. Most cases in the UK were relatively mild, although there were some serious cases.
The relatively small number of cases that led to serious illness or death were mostly in children and young adults – particularly those with underlying health problems – and pregnant women.
On 10 August 2010, the World Health Organization (WHO) declared the pandemic officially over.
«Swine flu» now
The A/H1N1pdm09 virus is now one of the seasonal flu viruses that circulate each winter. If you’ve had flu in the last few years, there’s a chance it was caused by this virus.
As many people now have some level of immunity to the A/H1N1pdm09 virus, it’s much less of a concern than it was during 2009 to 2010.
The symptoms are the same as other types of common flu. They’re usually mild and pass within 1 to 2 weeks. But as with all types of flu, some people are at higher risk of serious illness, particularly those with underlying health problems.
The regular flu jab will usually protect people who are at a higher risk of becoming severely ill. A vaccine programme for children has also been introduced, which aims to protect children and reduce their ability to infect others.
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Page last reviewed: 2 September 2020
Next review due: 2 September 2022
Key Facts About Swine Influenza
Get all of your questions answered about the swine flu, from common symptoms to treatment options.
By Everyday Health Editors
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What is swine influenza?
Swine influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus that regularly causes outbreaks of influenza in pigs. Swine flu viruses cause high levels of illness and low death rates in pigs. Swine influenza viruses may circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.
How many swine flu viruses are there?
Like all influenza viruses, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort (i.e. swap genes) and new viruses that are a mix of swine, human and/or avian influenza viruses can emerge. Over the years, different variations of swine flu viruses have emerged. At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H1N1 viruses.
Swine Flu in Humans
Can humans catch swine flu?
Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred. Most commonly, these cases occur in persons with direct exposure to pigs (e.g. children near pigs at a fair or workers in the swine industry). In addition, there have been documented cases of one person spreading swine flu to others. For example, an outbreak of apparent swine flu infection in pigs in Wisconsin in 1988 resulted in multiple human infections, and, although no community outbreak resulted, there was antibody evidence of virus transmission from the patient to health care workers who had close contact with the patient.
How common is swine flu infection in humans?
In the past, CDC received reports of approximately one human swine influenza virus infection every one to two years in the United States.
What are the symptoms of swine flu in humans?
The symptoms of swine flu in people are similar to the symptoms of regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea.
Can people catch swine flu from eating pork?
No. Swine influenza viruses are not transmitted by food. You can not get swine influenza from eating pork or pork products. Eating properly handled and cooked pork and pork products is safe. Cooking pork to an internal temperature of 160°F kills the swine flu virus, as it does other bacteria and viruses.
How does swine flu spread?
Influenza viruses can be directly transmitted from pigs to people and from people to pigs. Human infection with flu viruses from pigs are most likely to occur when people are in close proximity to infected pigs, such as in pig barns and livestock exhibits housing pigs at fairs. Human-to-human transmission of swine flu can also occur. This is thought to occur in the same way as seasonal flu occurs in people, which is mainly person-to-person transmission through coughing or sneezing of people infected with the influenza virus. People may become infected by touching something with flu viruses on it and then touching their mouth or nose.
What do we know about human-to-human spread of swine flu?
In September 1988, a previously healthy 32-year-old pregnant woman was hospitalized for pneumonia and died eight days later. A swine H1N1 flu virus was detected. Four days before getting sick, the patient visited a county fair swine exhibition where there was widespread influenza-like illness among the swine.
In follow-up studies, 76% of swine exhibitors tested had antibody evidence of swine flu infection but no serious illnesses were detected among this group. Additional studies suggest that one to three health care personnel who had contact with the patient developed mild influenza-like illnesses with antibody evidence of swine flu infection.
How can human infections with swine influenza be diagnosed?
To diagnose swine influenza A infection, a respiratory specimen would generally need to be collected within the first four to five days of illness (when an infected person is most likely to be shedding virus). However, some people, especially children, may shed virus for 10 days or longer. Identification as a swine flu influenza A virus requires sending the specimen to CDC for laboratory testing.
What medications are available to treat swine flu infections in humans?
There are four antiviral drugs that are licensed for use in the United States for the treatment of influenza: amantadine, rimantadine, oseltamivir and zanamivir. While most swine influenza viruses have been susceptible to all four drugs, the most recent swine influenza viruses isolated from humans are resistant to amantadine and rimantadine. At this time, CDC recommends the use of oseltamivir or zanamivir for the treatment and/or prevention of infection with swine influenza viruses.
What other examples of swine flu outbreaks are there?
Probably the most well known is an outbreak of swine flu among soldiers in Fort Dix, N.J. in 1976. The virus caused disease with X-ray evidence of pneumonia in at least four soldiers and one death; all of these patients had previously been healthy. The virus was transmitted to close contacts in a basic training environment, with limited transmission outside the basic training group. The virus is thought to have circulated for a month and disappeared. The source of the virus, the exact time of its introduction into Fort Dix, and factors limiting its spread and duration are unknown. The Fort Dix outbreak may have been caused by introduction of an animal virus into a stressed human population in close contact in crowded facilities during the winter. The swine influenza A virus collected from a Fort Dix soldier was named A/New Jersey/76 (Hsw1N1).
Is the H1N1 swine flu virus the same as human H1N1 viruses?
No. The H1N1 swine flu viruses are antigenically very different from human H1N1 viruses and, therefore, vaccines for human seasonal flu would not provide protection from H1N1 swine flu viruses.
Swine Flu in Pigs
How does swine flu spread among pigs?
Swine flu viruses are thought to be spread mostly through close contact among pigs and possibly from contaminated objects moving between infected and uninfected pigs. Herds with continuous swine flu infections and herds that are vaccinated against swine flu may have sporadic disease, or may show only mild or no symptoms of infection.
What are signs of swine flu in pigs?
Signs of swine flu in pigs can include sudden onset of fever, depression, coughing (barking), discharge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed.
How common is swine flu among pigs?
H1N1 and H3N2 swine flu viruses are endemic among pig populations in the United States and something that the industry deals with routinely. Outbreaks among pigs normally occur in colder weather months (late fall and winter) and sometimes with the introduction of new pigs into susceptible herds. Studies have shown that the swine flu H1N1 is common throughout pig populations worldwide, with 25 percent of animals showing antibody evidence of infection. In the United States studies have shown that 30 percent of the pig population has antibody evidence of having had H1N1 infection. More specifically, 51 percent of pigs in the north-central United States have been shown to have antibody evidence of infection with swine H1N1. Human infections with swine flu H1N1 viruses are rare. There is currently no way to differentiate antibody produced in response to flu vaccination in pigs from antibody made in response to pig infections with swine H1N1 influenza.
While H1N1 swine viruses have been known to circulate among pig populations since at least 1930, H3N2 influenza viruses did not begin circulating among U.S. pigs until 1998. The H3N2 viruses initially were introduced into the pig population from humans. The current swine flu H3N2 viruses are closely related to human H3N2 viruses.
Is there a vaccine for swine flu?
Vaccines are available to be given to pigs to prevent swine influenza. There is no vaccine to protect humans from swine flu. The seasonal influenza vaccine probably will help provide partial protection against swine H3N2, but not swine H1N1 viruses.