Influenza (Flu)

Influenza is a contagious disease caused by influenza viruses that infect the respiratory tract (nose, throat, and lungs). It can cause mild to severe illness, sometimes leading to death. Influenza symptoms often begin suddenly, with fever, headache, tiredness, dry cough, sore throat, nasal congestion, and body aches. The best way to prevent influenza is to get vaccinated each year.

Seasonal influenza refers to influenza strains that circulate each year and are most common during the winter months in Wisconsin. Avian influenza (bird flu) refers to influenza A viruses that usually infect birds, but can occasionally infect humans. Swine flu infections usually infect pigs and boars, however they can occasionally occur in humans.

Pandemic influenza is when a new (novel) and highly contagious influenza virus emerges and infects many people worldwide. Because humans have little natural immunity to this new virus, the disease can spread easily from person to person and sometimes can cause severe disease. The last influenza pandemic occurred during 2009-2010.

Weekly Influenza Report

Avian influenza 

Influenza A H3N2 variant viruses (H3N2v) (PDF,  43 KB)


Additional Info Group

Last Revised: May 18, 2015