The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat and lungs. It can cause mild to severe illness, and, at times, can lead to death. The best way to prevent the flu is by getting a flu vaccine each year.
People who have the flu often feel some or all of the following signs and symptoms:
It's believed that flu viruses spread mainly by droplets made when people with a flu cough, sneeze or talk. These droplets can land in the mouths or noses of people nearby. Less often, a person might also get flu by touching a surface or object that has flu virus on it, and then touching their own mouth, eyes or nose.
Most adults can infect others with the flu one day before symptoms develop and up to seven days after becoming sick. Even if a person shows no symptoms, they still may be able to spread the virus.
The first and most important step in preventing the flu is to get a flu vaccination every year. CDC also recommends everyday preventive actions such as staying away from people who are sick, covering coughs and sneezes, and frequent hand washing to help slow the spread of germs that cause respiratory illnesses like the flu.