What causes influenza?
Flu is caused by a virus in the body. It spreads when infected persons cough, sneeze, or even talk around others. People with flu are contagious a day before symptoms appear and three to seven days after. Children can be contagious for more than a week. You can get the flu simply by touching a surface like a telephone or doorknob that has been contaminated by a touch from someone who has the flu. The viruses can pass through the air and enter your body through your nose or mouth. If you have touched a contaminated surface, they can pass from your hand to your nose or mouth.
There are three types of influenza viruses. Type A is the most common flu. It changes often and causes a new epidemic, or mass outbreak of flu, every few years. An epidemic usually peaks within 2 or 3 weeks after the first cases occur. Type B causes smaller, local or regional outbreaks and Type C causes only mild illness.
To learn more:
- Colds and the Flu: Prevention
- This consumer health site from the American Association of Family Physicians gives good advice about coping with influenza and gives a simple explanation on what causes flu.
- Influenza (Flu): Causes
- This page from the Mayo Clinic’s influenza section explains the causes of flu. Click on other sections of the article for information about symptoms, risk factors, treatment, and prevention.