Overview

Noroviruses, including Norwalk, Snow Mountain, and Hawaii viruses, cause an illness in humans called gastroenteritis. Gastroenteritis is an inflammation of the stomach and intestines. Sometimes misnamed “stomach flu,” gastroenteritis is not related to flu (influenza), a respiratory illness caused by influenza virus.

Noroviruses are very contagious. They usually are found in contaminated food or drinks, but they also can live on surfaces or be spread through contact with an infected person. Each year in the United States, 23 million norovirus infections result in an estimated 50 thousand hospitalizations and 310 deaths, according to the Centers for Disease Control and Prevention (CDC).

Cause

The main viruses that cause gastroenteritis used to be called “Norwalk-like viruses” because Norwalk is the most well-known virus in this group. Now the viruses are referred to as noroviruses.

Noroviruses are not new, but interest in them is growing as researchers learn how frequently they make people sick. Norovirus infections are implicated in newsworthy descriptions of outbreaks on military and cruise ships and in hotels, restaurants, daycare centers, nursing homes, and hospitals. Decontamination of these places has proved to be challenging.

Noroviruses are not related to bacteria or parasites that also can cause gastrointestinal illnesses.

Transmission

You can get norovirus infection by

• Eating food or drinking liquids contaminated by a food handler infected with the virus
• Touching surfaces or objects contaminated with a norovirus, and then putting your hands in your mouth
• Having direct contact with someone infected with a norovirus, such as caring for or sharing food or eating utensils with someone sick with norovirus
• Eating improperly cooked contaminated shellfish, especially oysters
• Eating improperly prepared uncooked fruits and vegetables
• Drinking contaminated water

Noroviruses are found in the stool or vomit of people who are infected. If you have been infected with a norovirus, you can continue to transmit it to others even when you no longer have symptoms.

Symptoms

Because there are so many types of noroviruses, you can become infected and show symptoms many times. Symptoms of gastroenteritis caused by noroviruses can include

• Nausea
• Abdominal cramps
• Vomiting
• Diarrhea
• Headache
• Fatigue
• Fever
• Muscle aches

Symptoms usually develop within hours or a few days after you are infected with a norovirus. It usually takes a couple of days before you are better.

Diagnosis

Your health care provider can use laboratory tests to diagnose norovirus infection, but these tests are not used routinely. Usually, your health care provider will diagnose it by examining you and noting your symptoms.

Treatment

The best treatments for norovirus infection are to get plenty of bed rest and drink lots of fluids. To prevent dehydration (severe loss of body fluids), your health care provider may give you specific instructions about the type of fluids you should drink.

You should not take antibiotics for norovirus infection because they have no effect on viruses.

If your infant or child has diarrhea, you should contact a health care provider immediately for treatment advice.

Prevention

To prevent norovirus you should

• Wash your hands with soap and water frequently. This is especially important for food handlers and caregivers.
• Prepare fresh and frozen foods safely, including thoroughly washing fresh produce.
• Disinfect contaminated surfaces in your kitchen and bathrooms with household chlorine bleach-based cleaners to kill viruses resting on surfaces.
• Wash contaminated clothing, diapers, sheets, and towels promptly in hot water (above 140 degrees Fahrenheit) and/or with bleach.
• Choose wisely when eating or drinking outside your home. If you aren’t sure whether the food or water is safe, avoid it.

In addition, you should not prepare food for others if you have norovirus infection.

Currently, there is no vaccine to protect you from norovirus infections.