Norovirus

Fact Sheet about Noroviruses

What is norovirus?

Norovirus is a very contagious virus that causes acute gastroenteritis with vomiting and diarrhea. Gastroenteritis is inflammation of the stomach and intestines. While it is sometimes called the “stomach flu” or “stomach bug,” norovirus is not related to the flu, which is caused by the influenza virus.

How common is norovirus infection?

Norovirus is the leading cause of acute gastroenteritis among people of all ages in the United States.  It is possible to get sick at any time of the year, but illnesses are most common between November and April.

What are the symptoms of norovirus infection?

Common symptoms of norovirus infection come on suddenly and include vomiting, diarrhea, nausea, and abdominal cramps. People with norovirus can also experience fever, headache, and muscle aches. Symptoms usually begin 12 to 48 hours after exposure to the virus and last about 1 to 3 days in most people, with no long-term effects.

How is norovirus spread?

Noroviruses are very contagious and can be found in the stool or vomit of infected people.  People get sick by accidentally getting tiny particles of stool or vomit in their mouth from a person infected with norovirus. This can occur when people:

• Have direct contact with someone with norovirus;
• Eat food or drink liquids contaminated with norovirus;
• Eat uncooked shellfish that was harvested from contaminated waters; or
• Touch contaminated objects or surfaces and then touch their mouth or eat without washing their hands first.

Norovirus can spread quickly in crowded places such as healthcare facilities, restaurants, schools, child care facilities, and cruise ships.

Who gets norovirus infection?

Anyone can get infected with norovirus.  Children younger than 5 years old, older adults, and people with weakened immune systems are more likely to develop severe infections.

There are many strains of noroviruses, and being infected does not provide long-lasting immunity. People can become infected with norovirus many times during their life.

When is someone with norovirus contagious?

People with norovirus infection are most contagious when they have symptoms, especially vomiting, and during the first few days after feeling better. Studies have shown that you can still spread norovirus for two weeks or more after you feel better. Sometimes people infected with norovirus have no symptoms but can still pass the virus to others.

How is norovirus infection diagnosed?

Norovirus can be diagnosed by testing stool from an infected person. Many laboratories in Massachusetts are able to perform this test, but health care providers often base their diagnosis on a patient’s symptoms and how long they last.

What is the treatment for norovirus infection?

There is no specific treatment for norovirus infection. Norovirus cannot be treated with antibiotics and people usually get better without medical attention in 1 to 3 days. It is important for people infected with norovirus to drink plenty of liquids to replace fluids they have lost and prevent dehydration.

What can you do to prevent norovirus infection?

Take the following steps to prevent getting or spreading the disease:

• Wash your hands well and often with soap and water for at least 20 seconds, especially:
  • After using the toilet or changing diapers.
  • Before eating, preparing, or handling food.
  • Before giving yourself or someone else medicine.
• Be aware that hand sanitizer does not work well against norovirus.
• Handle and prepare food safely:
  • Wash fruits and vegetables well.
  • Cook food completely. Noroviruses are relatively resistant to heat and can survive temperatures as high as 145°F.
  • Cook oysters and other shellfish to an internal temperature of at least 145°F.
  • Routinely clean and sanitize kitchen utensils, cutting boards, counters, and surfaces.
• Disinfect frequently touched surfaces following instructions on the label of your cleaning product.
• When swimming or participating in recreational water activities, don’t swallow the water.

I have norovirus. How do I avoid spreading it to others?

• Stay home when you’re sick and until 24 hours have passed since your last vomiting episode, and your diarrhea has improved.
• Wash your hands often and well with soap and water for at least 20 seconds, especially after using the toilet or vomiting.
• Do not prepare or handle food, or care for others while you are sick and for at least 48 hours after symptoms stop.
• If you vomit or have diarrhea in a public toilet, such as one in a hospital, school, restaurant, or cruise ship, let the staff know so that they can properly clean and disinfect.
• Do not swim or participate in recreational water activities while sick with diarrhea.
• Clean and disinfect surfaces with a cleaning product effective against norovirus, such as a bleach solution, immediately after vomiting or diarrheal accidents.
  • To check if a cleaning product is effective against norovirus, find the EPA registration number on the product label (“EPA Reg. No.”) and search EPA’s Registered Antimicrobial Products Effective Against Norovirus (feline calicivirus) [List G]
  • Products that are effective against norovirus may list on the label that it is effective against norovirus or “feline calicivirus.”
  • Follow directions on the cleaning product’s label for use as a disinfectant product against norovirus, including how long the product needs to be left on a surface to be effective.
  • Follow instructions on your bleach bottle for preparing a diluted bleach solution.
• Wash laundry well that may be contaminated with vomit or stool.  Use detergent and the longest available wash cycle. Then machine dry at the highest heat setting.

Are there any restrictions for people with norovirus?

Yes. Workers in any food-related business who have norovirus must stay out of work for 72 hours after their symptoms have stopped. Food-related businesses include restaurants, sandwich shops, hospital kitchens, and grocery stores.  This requirement also applies to workers in schools, residential programs, daycares, and health care facilities who feed, give mouth care or dispense medications.

For more information contact:

• Your local board of health
• Your health care provider
• The Centers for Disease Control and Prevention (CDC) website
• Massachusetts Department of Public Health (DPH): Division of Epidemiology [phone] or on the DPH website