Individuals suffering from influenza are generally contagious for seven to nine days. Some people, such as those with compromised immune systems, have the potential to infect others for a longer period. Approximately 5 to 20 percent of Americans get the flu yearly, according to Flu.gov.
Seniors over the age of 65 and children under the age of 2 have an increased risk of developing the illness. Complications that may emerge from influenza include bacterial pneumonia, sinus infections and dehydration, notes Flu.gov. Seasonal flu typically reaches its climax in January or February, though the Centers for Disease Control and Prevention tracks flu-related phenomena in the United States from October to May.