Norovirus: The 'Stomach Bug' That Isn't Flu — How It Spreads and How to Stop It

Norovirus is the leading cause of vomiting and diarrhea, and of foodborne illness, in the United States. It is extremely contagious, and people of every age catch it.

People call it the "stomach flu" or "stomach bug," but it has nothing to do with influenza. It causes acute gastroenteritis — inflammation of the stomach or intestines.

What it's like

You can feel extremely ill, vomiting or having diarrhea many times a day.

You can catch it again and again

There are many types of norovirus, and being infected with one may not protect you from the others. People can build protection against specific types, but no one knows exactly how long it lasts — which may be why outbreaks sicken people of all ages. Your genes also partly decide how likely you are to be infected.

Watch for dehydration

Losing that much fluid can dehydrate you, especially young children, older adults and people with other illnesses. Signs:

• urinating less
• dry mouth and throat
• dizziness on standing up
• in children: crying with few or no tears, unusual sleepiness or fussiness

Drink plenty of liquids to replace what you lose. Sports drinks and other drinks without caffeine or alcohol help with mild dehydration but may not replace important nutrients and minerals; over-the-counter oral rehydration fluids work best. Severe dehydration can be serious and may need hospital treatment with IV fluids — if you think you or someone you're caring for is severely dehydrated, call your doctor.

Treatment

There is no specific medicine for norovirus. Antibiotics won't help — they fight bacteria, not viruses. Labs diagnose it by finding the virus's genetic material (RNA) or its antigen; all public health laboratories and many clinical labs can test for it.

How it spreads

Very easily, in several ways:

• Close contact with someone who has it — caring for them, sharing food or utensils, eating food they handled.
• Contaminated food or drink.
• Touching contaminated objects or surfaces, then putting unwashed fingers in your mouth.

Raw shellfish are a particular risk. Oysters and other filter-feeding shellfish can carry viruses and bacteria that cause illness or death when eaten raw, and anyone who eats raw shellfish can get norovirus. Children under 5, older adults and people with weakened immune systems are more likely to become severely ill. Don't eat raw or undercooked shellfish.

Prevention

• Wash your hands well and often — with soap and water, for at least 20 seconds.
• Cook shellfish thoroughly and wash fruits and vegetables.
• Clean and disinfect contaminated surfaces.
• Wash laundry in hot water.
• Stay home while sick, and for 2 days (48 hours) after symptoms stop.

CDC has more on how norovirus spreads, how to prevent it, when and how to wash your hands and norovirus facts for food workers.

Sources

Based on "About Norovirus," Centers for Disease Control and Prevention; a work of the United States government in the public domain. Two stock photographs are left out.