Typical clinical features of influenza may include

fever (usually 100 F-103 F in adults and often even higher in children, sometimes with facial flushing and/or sweating),

chills,

respiratory symptoms such as: cough (more often in adults), sore throat (more often in adults), runny or stuffy nose (congestion, especially in children), sneezing,

headache,

muscle aches (body aches), and fatigue, sometimes extreme.

    Although appetite loss, nausea, vomiting, and diarrhea can sometimes accompany influenza infection, especially in children, gastrointestinal symptoms are rarely prominent. The term "stomach flu" is a misnomer that is sometimes used to describe gastrointestinal illnesses caused by other microorganisms. H1N1 infections, however, caused more nausea, vomiting, and diarrhea than the conventional (seasonal) flu viruses. Depending upon the severity of the infection, some patients can develop swollen lymph nodes, muscle pain, shortness of breath, severe headaches, chest pain or chest discomfort, dehydration, and even death.

    Most individuals who contract influenza recover in a week or two, however, others develop potentially life-threatening complications like pneumonia. In an average year, influenza is associated with about 36,000 deaths nationwide and many more hospitalizations. Flu-related complications can occur at any age; however, the elderly and people with chronic health problems are much more likely to develop serious complications after the conventional influenza infections than are younger, healthier people.