What the Guidance Really Says About Norovirus

Key takeaways

• Symptoms start: 12 to 48 hours after exposure
• Usual length: 1 to 3 days
• Most useful single change: Sip water, oral rehydration solution or broth often to replace lost fluids.
• Commonest mistake: Cooking or serving food for others while sick and for 2 days afterward.
• See a doctor if any of the signs under "When to speak to a doctor" below apply to you.

What it is

A very contagious virus that causes sudden vomiting and diarrhea, often called the "stomach bug." It sits within Infectious Diseases. Below are the published figures, in one place.

The numbers, in one place

What helps

You do not have to do all of it, and you do not have to start today.

• Sip water, oral rehydration solution or broth often to replace lost fluids
• Wash hands with soap and water after using the toilet, changing diapers and before eating or cooking
• Wear disposable gloves to clean up vomit or diarrhea, then disinfect the area
• Wash soiled laundry on the longest hot cycle and machine dry it

What to avoid

Things that seem reasonable and are not.

• Cooking or serving food for others while sick and for 2 days afterward
• Relying on alcohol-based hand sanitizer instead of hand washing
• Sending children back to child care or school before your provider or program says it is safe

In depth

Norovirus infects the lining of the small intestine, damaging the tiny finger-like projections that absorb fluid and nutrients and disturbing how the gut moves. The result is a sudden burst of vomiting, watery diarrhea and cramps. In most healthy adults, the immune system clears the virus within a few days, but the rapid loss of fluid can cause dehydration, especially in young children, older adults and people with other health conditions.

Norovirus spreads so easily because very few virus particles are needed to make someone sick, while an infected person sheds huge numbers in vomit and stool. Vomiting can also send tiny droplets into the air and onto nearby surfaces. The virus can survive on countertops, doorknobs and fabrics for days, resists many common cleaners, and is not reliably killed by alcohol-based hand sanitizer.

There are many strains of norovirus, and immunity after infection does not last long, so you can catch it many times over your life. Outbreaks are common wherever people share close quarters, food or bathrooms: nursing homes, hospitals, cruise ships, schools, child care centers and restaurants. Most cases happen from November to April, which is why it is sometimes called winter vomiting disease.

Signs and symptoms

• Sudden nausea and vomiting, often forceful and without warning
• Watery diarrhea, usually without blood
• Stomach cramps and aching
• Low-grade fever, chills, headache and body aches
• Dry mouth and throat, dizziness on standing and passing little urine, which signal dehydration
• In young children, crying with few or no tears, fewer wet diapers or unusual sleepiness

Causes and risk factors

• Eating food handled by someone who is sick or did not wash their hands well
• Touching contaminated surfaces and then your mouth
• Caring for, or sharing food and utensils with, someone who is sick
• Eating raw or undercooked shellfish, especially oysters, from contaminated water
• Eating raw produce that was contaminated during growing, harvest or preparation
• Living in or visiting close-quarters settings during an outbreak

How it is checked

Norovirus is usually recognized from the pattern of symptoms, especially sudden vomiting and diarrhea that spreads through a household or group. Most people do not need a test, because the result would not change how they are cared for. When an outbreak is suspected in a restaurant, school or care facility, health departments may test stool samples to confirm the cause and trace the source.

Your doctor will focus on how dehydrated you are, checking things like heart rate, blood pressure, urine output and how alert you are. Blood tests, stool tests for other germs or imaging may be ordered if there is blood in the stool, a high fever, severe belly pain, symptoms lasting more than a few days, or a weakened immune system, to look for other causes.

Treatment and support options

Replacing fluids

Replacing what you lose is the most important treatment. Oral rehydration solutions from a pharmacy contain a balance of salt and sugar that helps the gut absorb water. After vomiting, wait a short while, then take small sips every few minutes and build up gradually. Adults can also use broth or diluted sports drinks; for young children, oral rehydration solution is best.

Getting back to eating

Once vomiting settles, start eating again when you feel ready. There is no need for a special or restricted diet; plain foods are often easiest at first. Breastfed babies should keep nursing, and formula-fed babies can continue formula. Avoid very sugary drinks such as juice and soda, which can pull water into the gut and worsen diarrhea.

Medical care for dehydration

If you cannot keep fluids down or show signs of dehydration, you may need care at urgent care or the ER. Doctors can give fluids through an IV and sometimes medicine to ease vomiting so you can drink again. Older adults and people taking diuretics or blood pressure medicines should ask whether to pause any medicines while ill.

Medicines to be careful with

Antibiotics do not work against norovirus. Over-the-counter anti-diarrhea medicines may help some adults with comfort, but they should not be given to young children unless a doctor advises it, and they should be avoided if there is a high fever or blood in the stool. Ask a pharmacist before using them.

Prevention

• Wash hands with soap and water, especially after using the toilet or changing diapers and before eating or cooking
• Cook oysters and other shellfish thoroughly
• Rinse fruits and vegetables before eating, cutting or cooking them
• Stay out of the kitchen for others while sick and for at least 2 days after symptoms stop
• Clean up vomit and diarrhea right away and disinfect the area
• Wash contaminated laundry promptly on a hot cycle

Day to day

When norovirus hits a household, plan for it to spread. If you can, give the sick person their own bathroom, keep everyone else's towels separate, and clean high-touch surfaces such as faucets, toilet handles and doorknobs daily. When cleaning up vomit, wear disposable gloves and a mask if you have one, use paper towels to remove the mess, then disinfect, and wash your hands well afterward.

Most people feel back to normal within a few days, though tiredness can linger. You can still shed the virus for two weeks or more after you feel better, so keep up careful hand washing. Food workers, health care workers and child care staff often have specific return-to-work rules; check with your employer or local health department.

For specific groups

Young children

Small bodies lose fluid quickly. Offer small amounts of oral rehydration solution often, count wet diapers, and watch for crying without tears or unusual sleepiness. Call your child's doctor if your child cannot keep fluids down or you are worried about dehydration.

Older adults

Older adults are more likely to become dehydrated and to need hospital care. Confusion, dizziness or falls can be early signs. In nursing homes and assisted living, outbreaks are handled with extra cleaning, keeping sick residents apart and limiting group activities.

Weakened immune systems

People with weakened immunity, such as transplant recipients, can have diarrhea that lasts for weeks or months. Tell your specialist if symptoms continue beyond a few days, since your care may need to be adjusted.

Questions to ask your doctor

• How can I tell if my child or I am getting dehydrated?
• Should I stop any of my regular medicines while I am sick?
• When is it safe to go back to work, school or child care?
• Do I need a stool test?
• Is an anti-nausea or anti-diarrhea medicine appropriate for me?

More questions, answered

Is norovirus the same as food poisoning?

Norovirus is the leading cause of foodborne illness in the US, but it also spreads directly from person to person and through contaminated surfaces. Other germs, such as Salmonella and E. coli, can also cause food poisoning, often with fever or bloody diarrhea, and some of those need different care.

Is there a vaccine for norovirus?

Not yet. Vaccines are being studied, but none is currently available in the US. Prevention depends on hand washing, careful food handling, cleaning and staying home while sick.

How long am I contagious?

You are most contagious while you are sick and in the first few days after you recover. The virus can remain in stool for two weeks or more, so keep washing your hands carefully with soap and water, especially before handling food for others.

Why does hand sanitizer not work well?

Norovirus lacks the fatty outer coat that alcohol damages in many other viruses, so it is more resistant. Washing with soap and water for at least 20 seconds physically removes virus particles, which is why it is recommended over sanitizer alone.

Can I get norovirus from my pet?

Human norovirus is not known to be spread by pets. Pets can still track contaminated material around the house, so keep them away from areas that are being cleaned up after vomiting or diarrhea.

Should I stop eating out during outbreaks?

Not usually. Restaurants are required to follow food safety rules, including keeping sick workers home. If you hear of an outbreak linked to a specific place, follow health department advice, and always wash your hands before eating.

Related topics

• The Evidence on Infection Prevention at Home, Without the Hype (Immunity)
• What the Guidance Really Says About Diarrhea (Digestive Health)
• Travelers' Diarrhea: What the Evidence Actually Says (Travel Health)
• Common Childhood Infections: What the Evidence Actually Says (Children's Health)

Where to go next

• Norovirus: Common Questions Answered
• Norovirus at a Glance
• Norovirus — the reference entry
• Infectious Diseases: The Complete Guide
• Strep Throat: What Published Guidance Supports
• Hepatitis A: Sorting the Evidence From the Noise

When to speak to a doctor

Call your doctor if vomiting or diarrhea lasts more than a few days, there is blood in the stool, or a baby, older adult or someone with a chronic condition cannot keep fluids down. Call 911 for signs of severe dehydration, such as very little or no urine, dizziness when standing, fainting, confusion, or a child who is unusually sleepy or fussy and cries without tears.

Where this comes from

• CDC — About Norovirus
• EPA — List G: EPA's Registered Antimicrobial Products Effective Against Norovirus

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.