It spreads from one infected person to another. It can cause fever, chills, headache, cough, sore throat, and muscle aches.
Flu can lead to pneumonia and death.
Flu can affect people of any age. Occasionally people with flu will need to be hospitalized. Thousands of people die each year from flu-related illnesses. Most deaths caused by flu occur in the elderly population. The viruses that cause influenza change often, therefore a new vaccine is developed each year.