Influenza

Influenza (the flu) is a contagious respiratory illness caused by influenza viruses.  Every year in the United States, on average 5% to 20% of the population gets the flu; more than 200,000 people are hospitalized and 36,000 people die from seasonal flu complications. There are three types of influenza viruses: A, B and C. Influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics.

Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes, Influenza A viruses can be further broken down into different strains. The current subtypes of influenza A viruses found in people are A (H1N1) and A (H3N2).  Influenza B viruses are not divided into subtype, but can be further broken down into different strains. Influenza A (H1N1), A (H3N2), and influenza B strains are included in each year's influenza vaccine. Getting a flu vaccine can protect against influenza A and B viruses. The flu vaccine does not protect against influenza C viruses.

Studies have shown that human influenza viruses generally can survive on inanimate items/surfaces for between 2 and 8 hours. Influenza virus is only destroyed by heat between 167-212°F or 75-100°C (CDC, 2009).