Sudden fever and chills, muscle aches, headache, tiredness, sore throat, congestion. If you have these, you likely have the flu. Between 3% and 11% of people in the U.S. get it each year. It usually clears up within 2 weeks, but you may be tired for a while. For small children, the elderly, and those with weak immune systems, it can be dangerous and even deadly. If you’re at risk for complications or very sick, your doctor may give you antiviral medicine. The best way to keep from getting it is to get a flu shot every year.