Norovirus

Photo of a norovirus
Photograph of noroviruses

Image/CDC

What is norovirus?
Noroviruses are a very contagious viruses that can affect anyone, causing acute gastroenteritis that some people have called the "stomach flu" (although norovirus is not related to the influenza/flu virus). Handwashing and environmental cleaning are essential to stopping its spread.

What are the symptoms of norovirus?
Symptoms usually develop 12-48 hours after being exposed and include nausea, vomiting,
and watery diarrhea with abdominal cramps. Some people may have low-grade fever,
headaches, and body aches. Symptoms usually last from 24-72 hours, and most people
recover completely. However, some people can get very dehydrated, especially young
children, the elderly, and people with underlying illnesses.

How long are people infectious?
Norovirus can be found in your stool (feces) even before you start feeling sick and can stay
in your stool for 2 weeks after you feel better. However, you are most contagious when you
are sick and during the first few days after you recover.

How is norovirus spread?
Noroviruses are found in the stool or vomit of infected people, and people with norovirus
illness can shed billions of virus particles. People can become infected with the virus
in several ways, including:
• Close personal contact with a person who is infected.
• Consuming food or drinks that are contaminated with norovirus.
• Touching surfaces, objects, or substances contaminated with norovirus and then
placing one’s hand in one’s mouth
• Swallowing aerosolized vomit that enters a person’s mouth
Environmental surfaces (including furniture, railings, doorknobs, carpeting, etc.) can
very easily become contaminated with norovirus because the virus is so small and
because it can be infectious at a very low dose (it takes fewer than 20 norovirus particles
to make a person sick).

How is norovirus diagnosed?
Testing for norovirus involves a stool sample and is usually only done when there is an
outbreak of gastrointestinal illness in order to identify the cause.

How can norovirus be prevented?
There is no vaccine to prevent norovirus infection. These are the best ways to prevent
infection:
• Wash your hands carefully with soap and water, especially after using the toilet,
changing a diaper, and before eating, preparing, or handling food. Alcohol-based hand
sanitizers may be used in addition to hand washing, but they should not be used as a
substitute for washing with soap and water.
• Clean and disinfect contaminated surfaces, counters, and utensils.
• Immediately remove and wash clothing or linens that may be contaminated with
virus after an episode of illness, wash with hot water and detergent, and dry them at the
highest temperature as soon as possible.
• Flush or discard any vomit and/or stool in the toilet and make sure that the surrounding
area is kept clean.
• If preparing foods, wash fruits and vegetables well and cook seafood thoroughly.
• If you are sick, do not prepare food or care for others.

Are there special guidelines for food workers or people handling food?
Yes. Because norovirus is often spread by infected food workers, it is essential that food
workers strictly follow prevention measures (described above). Food workers may not
contact exposed, ready-to-eat food with their bare hands and shall use suitable utensils,
such as deli tissue, spatulas, tongs, single-use gloves, or dispensing equipment. In addition,
sick food workers should wait at least 48 hours after recovering from any gastrointestinal
illness before returning to work.

Can norovirus be treated?
Antibiotics will not help with norovirus, because antibiotics are not effective against
viruses. If you have norovirus illness, drink plenty of liquids to replace fluid loss and
prevent dehydration. If you, or someone you are caring for, begin to become dehydrated,
call a healthcare provider.

Can a person have norovirus more than once?
Yes. Because there are many types of norovirus, the immunity that a person develops to
one type will not protect against another type. Also, it is not known how long the immunity
lasts.

How should outbreaks be reported?
Gastrointestinal illness thought possibly acquired in a park should be reported to the
park’s Public Health Consultant, the NPS medical epidemiologist, Dr. Maria Said (202-
513-7151), or the NPS One Health Coordinator, Dr. Danielle Buttke (970-267-2118).

Where can I get more information?
More information on norovirus is also available at www.cdc.gov/norovirus.