H3N2v and You

What is H3N2v?

H3N2v is a non-human influenza virus that normally circulates in pigs and that has infected humans. Viruses that normally circulate in pigs are “swine influenza viruses.” When these viruses infect humans, they are termed “variant” viruses.

In 2011, a specific H3N2 virus was detected with genes from avian, swine and human viruses and the 2009 H1N1 pandemic virus M gene. The virus was circulating in pigs in 2010 and was first detected in people in 2011.The acquisition of the 2009 M gene may make this virus infect humans more easily than is typical for other swine influenza viruses. There were 12 human infections with this virus, termed H3N2v, in 2011; most were associated with exposure to pigs. In 2012, H3N2v outbreaks in humans associated with exposure to pigs began in July.

See Case Count: Detected U.S. Human Infections with H3N2v by State since August 2011 for information about H3N2v cases, hospitalizations and deaths that have been reported to CDC.

How can a person catch a flu virus from a pig?

Influenza viruses can spread from pigs to people and from people to pigs. Spread from infected pigs to humans is thought to happen in the same way that seasonal influenza viruses spread between people; mainly through infected droplets created when an infected pig coughs or sneezes. If these droplets land in your nose or mouth, or you inhale them, you can be infected. There also is some evidence that you might get infected by touching something that has virus on it and then touching your own mouth or nose. A third possible way to get infected is to inhale dust containing influenza virus. Scientists aren’t really sure which of these ways of spread is the most common.

What are the symptoms of H3N2v?

Symptoms of H3N2v infection are similar to those of seasonal flu viruses and can include fever and respiratory symptoms, such as cough and runny nose, and possibly other symptoms, such as body aches, nausea, vomiting, or diarrhea.

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Why is CDC concerned about H3N2v?

CDC is concerned about H3N2v for a few reasons.

First, infections with influenza viruses (including variant viruses like H3N2v) can sometimes cause severe disease, even in healthy people. This can include complications (like pneumonia), which can require hospitalization, and sometimes result in death.

Second, this virus seems to spread more easily to humans from pigs than other swine influenza viruses.

Third, influenza viruses are always changing. It’s possible the H3N2v virus could change and begin spreading easily from person to person.

Fourth, studies conducted by CDC have indicated that children younger than 10 years old have little to no immunity against H3N2v virus. (Adults might have more immunity, perhaps because they might have been exposed to similar viruses in their longer lifetimes.)

Is H3N2v dangerous?

Currently, the severity of human illness associated with H3N2v resembles that of seasonal flu.

Keep in mind that even seasonal influenza can be a serious disease. Sometimes seasonal influenza can lead to complications (like pneumonia). It also can lead to hospitalization and even death.

Is there a vaccine for H3N2v?

Early steps to make a vaccine against H3N2v have been taken, but no decision to mass produce such a vaccine has been made.

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Will this season’s flu vaccine protect me against H3N2v?

The 2012-2013 seasonal flu vaccine will not protect against H3N2v. The seasonal flu vaccine will protect you against seasonal influenza viruses that are expected to circulate this season. CDC recommends that everyone 6 months and older get a seasonal flu vaccine each year.

Is there treatment for H3N2v?

Yes. The same influenza antiviral drugs used to treat seasonal flu can treat H3N2v in children and adults. The currently recommended drugs – oseltamivir and zanamivir - are available by prescription from your doctor.

Early treatment works better and may be especially important for people with a high risk condition.

If you are prescribed antiviral drugs by your doctor, you should finish all of the medication, according to your doctor’s instructions.

Who is at high risk of serious H3N2v illness?

People who are at high risk of developing complications if they get seasonal flu include the following: children younger than 5 years, people 65 years and older, pregnant women, and people with certain long-term health conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions).

(A full list of people at high risk of flu related complications is available at People at High Risk of Developing Flu-Related Complications.) These same groups of people are thought to be at high risk of developing serious complications from H3N2v infection.

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Can I get H3N2v from eating pork?

No. Influenza viruses have not been shown to be transmissible to people through eating pork (pig meat).

When did H3N2v start? How many people have been infected?

The H3N2v virus was found in U.S. pigs in 2010 and in people in 2011.

Between August and December 2011, 12 U.S. residents were found to be infected with H3N2v.

In April 2012, a case of H3N2v was detected in a child. Beginning in July 2012, many more cases of H3N2v associated with swine exposure at agricultural fairs were reported to CDC by different states.

See Influenza A (H3N2) Variant Virus Outbreaks for the latest information regarding the number of cases, hospitalizations and deaths reported to CDC.

Who has been infected by H3N2v?

Most H3N2v infections have occurred in children with exposure to swine; many have occurred at agricultural fairs.

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What is CDC doing about this situation?

CDC is communicating regularly with states, and states have ramped up their surveillance and laboratory activities to detect human cases of H3N2v.

CDC also is monitoring the situation closely. CDC’s Influenza Division is examining the genes of many of the H3N2v viruses that are shipped by state public health laboratories to CDC, to ensure that the virus is not changing in key ways. To date, no significant changes in the H3N2v virus have been detected.

What should I do if I am at an agricultural fair?

See Take Action to Prevent the Spread of Flu Between People and Pigs at Fairs for a list of steps you can take to protect yourself against H3N2v.

In particular, if you are at high risk of serious flu complications, avoid pigs and swine barns at the fair this year.

Should I avoid agricultural fairs where swine are present?

It’s not necessary to avoid agricultural fairs where swine are present. However, you should take steps to protect yourself against H3N2v if you do attend agricultural fairs, particularly where swine are present.

If you are at high risk of serious flu complications, avoid pigs and swine barns at the fair this year.

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Should people avoid pigs and swine barns?

People with health or age factors that put them at high risk for serious flu complications should avoid pigs and swine barns this year.

Are there things I should do, even if I’m not around pigs?

As always, take time to get a seasonal influenza vaccine as soon as flu vaccine becomes available in your community, to protect yourself from the seasonal influenza viruses that are most likely to circulate this season.

Can you tell if a pig has the flu?

No, you cannot always tell if a pig has a flu virus, just by looking at the pig. Some pigs infected with influenza may have no symptoms at all. See Key Facts About Swine Influenza (Swine Flu) in Pigs for a list of signs of flu in pigs.

Is H3N2v the same as the H3N2 flu virus that makes people sick each flu season?

No, H3N2v is different. H3N2v is a variant virus that is spreading in pigs and has infected some humans.

H3N2, also called seasonal influenza A(H3N2), is a human seasonal influenza virus that circulates among people each influenza season in the United States. The 2012-2013 seasonal influenza vaccine provides protection against seasonal influenza A(H3N2). See What You Should Know for the 2012-2013 Flu Season for information about this year’s seasonal flu vaccine.

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