Norovirus is a highly contagious virus that causes inflammation in the stomach and intestines, a condition known as gastroenteritis. It is the leading cause of vomiting and diarrhea, and foodborne illness in the United States. Norovirus is sometimes called the “stomach flu” or “stomach bug,” but it is not related to the flu, which is caused by influenza virus.

Norovirus spreads easily through close contact with an infected person, contaminated food or water, or contaminated surfaces. Symptoms of norovirus infection usually start suddenly and include nausea, vomiting, stomach pain or cramps, watery or loose diarrhea, feeling ill, low-grade fever, and muscle pain. The illness often begins suddenly, and infected people generally recover in one to two days. However, for some people, especially young children, older adults, and people with weakened immune systems or other medical conditions, vomiting and diarrhea can be severely dehydrating and require medical attention.

To protect yourself and others from norovirus, it is important to wash your hands thoroughly with soap and water, especially after using the bathroom or changing diapers, before eating, preparing, or handling food, and before giving yourself or someone else medication. You should also avoid preparing food or caring for others when you are sick, carefully wash fruits and vegetables before preparing and eating them, and cook oysters and other shellfish before eating them. Alcohol-based hand sanitizers can be used in addition to hand washing with soap and water, which is more effective at removing norovirus particles.