Influenza spreads rapidly to others through sneezing, coughing, or direct contact with the infected individual or contaminated objects.
Symptoms begin one to five days after exposure.
Complications such as pneumonia or dehydration may occur, especially in children, elderly persons, and persons with chronic illnesses. For healthy children and adults, influenza is typically a moderate to severe illness. Major symptoms usually are better within a week. Severe complications may occur in people who are elderly, frail or have chronic health problems such as diabetes, asthma, heart or lung problems, occasionally resulting in death. Pregnant women who get the flu during their second or third trimester of pregnancy have an increased risk of complications.