This results in a new epidemic every few years. Types B and C are not as widespread. Type B can cause smaller, more localized outbreaks. Type C is less common and usually causes only mild illness. All symptoms are usually gone within 7 to 14 days.
Influenza is spread by virus-infected droplets coughed or sneezed into the air.
People infected with the flu are contagious as long as they show symptoms. The flu usually occurs in small outbreaks, but epidemics tend to occur every few years. Epidemics peak within 2 or 3 weeks after the first cases occur and then begin to subside. Symptoms usually appear 1 to 4 days after a person is exposed to the flu virus. This is easier said than done, of course.