Influenza produces marked upper respiratory as well as general body symptoms. The strains of these viruses that are responsible for large outbreaks of illness change from year to year. The U.S. Public Health Service monitors influenza activity and predicts viral strains that can be expected each year. The influenza vaccine components are based on these predictions.
Many people also have a sore throat and runny nose.
Although you may have a loss of appetite, influenza virus does not usually give you gastrointestinal symptoms such as vomiting and diarrhea. Severe symptoms usually last 3 to 7 days, however, cough and fatigue may persist for several weeks. The influenza virus is spread through secretions from the nose and throat of currently ill people. The period of communicability is probably limited to the first 3 days of illness and the incubation period is 24-72 hours. Good handwashing before touching your eyes, nose, or mouth with your hands can help to decrease the chance of acquiring influenza.