Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness. The best way to prevent flu is by getting a flu vaccine each year.
Flu can cause mild to severe illness. Flu is different from a cold. Flu usually comes on suddenly. People who have flu often feel some or all of these symptoms:
- sore throat
- runny or stuffy nose
- body aches
- sometimes diarrhea and vomiting
*It’s important to note that not everyone with flu will have a fever.
How Flu Spreads
Most experts believe that flu viruses spread mainly by tiny droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose or possibly their eyes.
Period of Contagiousness
You may be able to pass on flu to someone else before you know you are sick, as well as while you are sick.
- People with flu are most contagious in the first 3-4 days after their illness begins.
- Some otherwise healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick.
- Some people, especially young children and people with weakened immune systems, might be able to infect others with flu viruses for an even longer time.