About Norovirus

Key points

  • Norovirus is the leading cause of vomiting and diarrhea, and foodborne illness in the United States.
  • People of all ages can get infected and sick with norovirus.
  • Proper handwashing and other simple steps can help prevent getting and spreading norovirus.
Father helps son wash vegetables.

What it is

Norovirus is a very contagious virus that causes vomiting and diarrhea.

It is sometimes called the "stomach flu" or the "stomach bug." However, norovirus illness is not related to the flu. The flu is caused by the influenza virus. Norovirus causes acute gastroenteritis, an inflammation of the stomach or intestines.

Most people with norovirus illness get better within 1 to 3 days; but they can still spread the virus for a few days after.


You can get norovirus illness many times in your life because there are many different types of noroviruses. Infection with one type of norovirus may not protect you against other types.

It is possible to develop protection against specific types. But it is not known exactly how long protection lasts. This may explain why so many people of all ages get infected during norovirus outbreaks.

Signs and symptoms

A person usually develops symptoms 12 to 48 hours after being exposed to norovirus.

  • Most common symptoms: Diarrhea, vomiting, nausea, stomach pain
  • Other symptoms: Fever, headache, and body aches


If you have norovirus illness, you can feel extremely ill, and vomit or have diarrhea many times a day. This can lead to dehydration (loss of body fluids), especially in young children, older adults, and people with other illnesses. Symptoms of dehydration include:

  • Decreased urination
  • Dry mouth and throat
  • Feeling dizzy when standing up
  • Crying with few or no tears
  • Unusual sleepiness or fussiness

Who is at risk

Anyone can get infected and sick with norovirus and people of all ages get infected during norovirus outbreaks. Your likelihood of getting a norovirus infection is also determined in part by your genes.

If eaten raw, oysters and other filter-feeding shellfish can contain viruses and bacteria that can cause illness or death. Anyone who consumes raw shellfish is at risk of contracting norovirus. Children younger than 5 years old, older adults, and people with weakened immune systems are more likely to develop severe infections.

Raw oysters on a plate with lemon.
To avoid getting norovirus, do not eat raw or undercooked shellfish.

How it spreads

Norovirus spreads very easily and quickly in different ways. You can get norovirus by:

  • Having direct contact with someone with norovirus, like caring for them, sharing food or eating utensils with them, or eating food handled by them.
  • Eating food or drinking liquids that are contaminated with norovirus.
  • Touching contaminated objects or surfaces and then putting your unwashed fingers in your mouth.

You can still spread norovirus for 2 weeks or more after you feel better.

Keep Reading: How Norovirus Spreads


Norovirus is very contagious, but you can take steps to protect yourself and others, including:

  • Wash your hands well and often.
  • Cook shellfish thoroughly and wash fruits and vegetables.
  • Clean and disinfect contaminated surfaces.
  • Wash laundry in hot water.
  • Stay home when sick for 2 days (48 hours) after symptoms stop.
Wash your hands after changing diapers, touching common surfaces, shanking hands, caring for the sick. Prevent norovirus.
Wash your hands often with soap and water for at least 20 seconds.

Testing and diagnosis

Diagnostic methods for norovirus focus on detecting viral RNA (genetic material) or viral antigen. Diagnostic tests are available at all public health laboratories and many clinical laboratories.

Treatment and recovery

Most people with norovirus illness get better within 1 to 3 days. There is no specific medicine to treat people with norovirus illness. Antibiotic drugs will not help treat norovirus infections because they fight bacteria, not viruses.

Watch for dehydration

Watch for signs of dehydration (loss of body fluids) in children who have norovirus illness. Children who are dehydrated may cry with few or no tears and be unusually sleepy or fussy.

Drink plenty of liquids

If you have norovirus illness, you should drink plenty of liquids to replace fluid lost from vomiting and diarrhea. This will help prevent dehydration.

Sports drinks and other drinks without caffeine or alcohol can help with mild dehydration. However, these drinks may not replace important nutrients and minerals. Oral rehydration fluids that you can get over the counter are most helpful for mild dehydration.

Seek medical care for severe dehydration

Dehydration can lead to serious problems. Severe dehydration may require hospitalization for treatment with fluids given through your vein (intravenous or IV fluids). If you think you or someone you are caring for is severely dehydrated, call your doctor.