Noroviruses are a group of viruses (previously known as Norwalk-like viruses) that can cause gastroenteritis, an inflammation of the stomach and intestines. Norovirus is the leading cause of foodborne illness.

This infection is often mistakenly referred to as the “stomach flu”. Norovirus is not related to the flu (influenza), which is a common respiratory illness caused by the influenza virus.

Norovirus infection occurs most frequently in closed and crowded environments. Examples include hospitals, nursing homes, child care centers, schools and cruise ships.

What are the symptoms?

Common symptoms of norovirus infection include vomiting, diarrhea, and stomach cramping. Less common symptoms can include low-grade fever or chills, headache, and muscle aches. Symptoms usually begin 1 or 2 days after ingesting the virus, but may appear as early as 12 hours after exposure. The illness typically comes on suddenly. The infected person may feel very sick and vomit often, sometimes without warning, many times a day. Sometimes people infected with norovirus have no symptoms at all, but can still pass the virus to others.

Prevention

Washing your hands thoroughly with soap and water is the best way to protect yourself and others from norovirus. It is especially important to wash your hands after using the bathroom or changing diapers; before eating, preparing, or handling food; and before giving yourself or someone else medicine. Avoid preparing food or caring for others when you are sick. Always carefully wash fruits and vegetables before preparing and eating them. Cook oysters and other shellfish before eating them.

Alcohol-based hand sanitizers can be used in addition to, but are not a substitute for, hand washing with soap and water, which is more effective at removing norovirus particles.

After someone vomits or has diarrhea, it is important to clean and disinfect. Wear rubber or disposable gloves and wipe the entire area with paper towels. Then disinfect the area using a bleach-based household cleaner as directed on the product label. Be sure to clean soiled laundry, take out the trash, and wash your hands.

No vaccines are currently available to prevent norovirus, although research is underway.

Treatment

If you have norovirus illness, drink plenty of liquids to prevent dehydration which can lead to serious problems. If you think you or someone you are caring for is severely dehydrated, call a healthcare professional.

There are no specific medicines to treat people with norovirus. Antibiotics do not help because they fight bacteria, not viruses.