The influenza virus or “flu” is a respiratory virus that circulates in Ontario, most frequently in the fall and winter. Influenza spreads from person-to-person through coughing, sneezing or having face-to-face contact. It can cause mild to severe respiratory disease. While anyone can get influenza, the very young, the elderly and people with certain medical conditions are at higher risk of complications. The best way to prevent infection is to receive the seasonal influenza vaccine every year.