Influenza (flu) is a seasonal disease that can cause mild to severe illness. Most experts think flu viruses are spread mainly by droplets when people with flu cough, sneeze or talk. Less often, a person might also get the flu by touching a surface or object that has the flu virus on it and then touching their own mouth or nose.
People can spread the flu even if they don't know they’re sick. The flu can be more serious for some people, including young children, pregnant women, older people, people with certain health conditions and smokers. The best way to prevent the flu is by getting vaccinated each year.