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About Seasonal Flu - FAQs:
When is the flu season in the United States?
In the United States, the peak of flu season has occurred anywhere from late November through March. The overall health impact (e.g., infections, hospitalizations, and deaths) of a flu season varies from year to year. CDC monitors circulating flu viruses and their related disease activity and provides influenza reports each week from October through May.
To learn about where the flu is spreading (by region), see the Flu Activity and Surveillance CDC site: http://www.cdc.gov/flu/weekly/fluactivitysurv.htm.
What is seasonal influenza (flu)?
Seasonal influenza, commonly called "the flu," is caused by influenza viruses, which infect the respiratory tract (i.e., the nose, throat, lungs). Unlike many other viral respiratory infections, such as the common cold, the flu can cause severe illness and life-threatening complications in many people.
In the United States, on average 5% to 20% of the population gets the flu; more than 200,000 people are hospitalized from seasonal flu-related complications, and; about 23,600 people die from seasonal flu-related causes. Some people, such as older people, young children, pregnant women, and people with certain health conditions, are at high risk for serious flu complications.
What sort of flu season is expected this year?
Flu seasons are unpredictable in a number of ways. Although epidemics of flu happen every year, the timing, severity, and length of the epidemic depends on many factors, including what influenza viruses are spreading and whether they match the viruses in the vaccine.
The 2009-2010 season saw the emergence of the 2009 H1N1 influenza virus (previously called "novel H1N1" or "swine flu"). This virus caused the first influenza pandemic (global outbreak of disease caused by a new flu virus) in more than 40 years. While not certain, it is likely that 2009 H1N1 viruses will continue to spread for a third year along with seasonal viruses in the U.S. during the 2011-2012 flu season.
Will new strains of flu circulate this season?
Flu viruses are constantly changing, so it's not unusual for new flu virus strains to appear each year. For more information about how flu viruses change, visit “How Can the Flu Virus Change.”
While not certain, it is likely that 2009 H1N1 viruses and seasonal viruses will cause illness in the U.S. during the 2011-2012 flu season.
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