Statement – After causing the 2009 pandemic, A(H1N1) circulates as a seasonal human influenza virus. The influenza vaccine will protect against it

Statement by Dr Nedret Emiroglu, Director Communicable Diseases and Health Security, WHO Regional Office for Europe


The A(H1N1) virus – causing what was commonly called "swine flu" in the past – caused an influenza (flu) pandemic in 2009, and has continued to circulate since then as a seasonal human flu virus. 

In 2009, the world's population had little immunity to A(H1N1) because it was new. Thus, it caused a global epidemic, with 100 000–400 000 estimated deaths that year alone. 

After 2009, A(H1N1) started circulating as an annual seasonal flu virus, along with the A(H3N2) and B viruses, although different viruses can predominate in each flu season. In the 2015–2016 season, several countries in the European Region are experiencing severe cases and deaths due to A(H1N1).

No evidence that seasonal A(H1N1) is more harmful than the pandemic virus 

Seasonal A(H1N1) has not changed significantly from the 2009 pandemic virus. 

Since its emergence in 2009, A(H1N1) has been known to cause severe disease in otherwise healthy, younger adults, in contrast to the A(H3N2) virus, which causes severe disease and death especially in elderly people. Countries where the A(H1N1) virus is circulating can expect an increase in the level of severe disease and death in young, otherwise healthy adults, including pregnant women. 

Current flu vaccine expected to provide good protection 

Each season, a flu vaccine is developed to protect against the viruses that research suggests will circulate. The vaccine for the 2015–2016 season in the northern hemisphere includes A(H1N1), A(H3N2) and B virus strains. 

There are indications that this season's vaccine is a good match with most of the seasonal flu viruses: that is, the viruses in the vaccine are closely related to those circulating among people. The current vaccine is therefore expected to provide good protection. 

As certain groups of people are at higher risk of severe disease, we at WHO strongly recommend that they be vaccinated against flu every year. These include people aged over 65, residents of institutions for older and disabled people, pregnant women, anyone with chronic conditions such as heart or lung disease or chronic neurological conditions, and children aged 6–59 months. 

People with severe or unusual flu-like symptoms should contact their physicians 

No matter the type of flu virus involved, flu is always unpleasant, but it is usually mild, and most people recover quickly. People with symptoms such as coughing, sneezing, sore throat, headache and a slight temperature can rest at home and visit a local pharmacy for advice and/or to get some painkillers and decongestants. 

People who develop any severe symptoms, do not improve within 72 hours from their onset or are at increased risk of severe disease should consult their physicians, so that treatment with antiviral drugs (oseltamivir or zanamivir) can start as early as possible. Such treatment should not be delayed to wait for the results of flu tests.