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.