Stomach flu: How long am I contagious?

It depends on which virus is causing your stomach flu (viral gastroenteritis). A number of viruses can cause gastroenteritis, including noroviruses and rotaviruses. The contagious period — the time during which a sick person can give the illness to others — is slightly different for each virus.

Norovirus is the most common cause of viral gastroenteritis in adults. Symptoms appear within one to three days of exposure. With norovirus, you're contagious from the moment you begin to feel ill. Although you typically feel better after a day or two, you're contagious for at least three days after you've recovered. Some people may be contagious for up to two weeks after recovery. Also, children are often contagious for a longer period than are adults.

Rotavirus is the leading cause of viral gastroenteritis in infants and young children. Symptoms of rotavirus appear one to two days after exposure. But you're contagious even before you develop symptoms, and you typically remain contagious for two weeks after you've recovered. Children are often contagious for a longer period than are adults.

For these reasons, it's important to wash your hands frequently and thoroughly — whether you feel ill or not. The viruses that cause gastroenteritis are spread through close contact with infected persons, such as by sharing food or eating utensils. Washing your hands is the most effective way to stop the spread of these viruses to others.