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Norovirus is the leading cause of foodborne illness in the United States, responsible for approximately 58% of cases. It is also a primary cause of acute gastroenteritis, leading to symptoms such as vomiting and diarrhea.
Norovirus can infect people of all ages, causing illness regardless of age.
Washing hands properly and following simple hygiene practices can help prevent the spread of norovirus.
Norovirus is a highly contagious virus that leads to vomiting and diarrhea.
Often referred to as the “stomach flu” or “stomach bug,” norovirus is not related to influenza, which is caused by the flu virus. Instead, it causes acute gastroenteritis, an inflammation of the stomach and intestines.
Most people recover within 1 to 3 days, but they can continue spreading the virus for several days after their symptoms improve.
If you have norovirus, you typically do not need to see a doctor, as it usually resolves on its own within a few days. However, if you experience severe dehydration, persistent vomiting, high fever, or prolonged diarrhea, you should visit a primary care doctor, urgent care, or a gastroenterologist (a specialist in digestive health).
For children, the best option is a pediatrician, especially if symptoms are severe. If dehydration becomes serious, an emergency room visit may be necessary.
Yes, you can get norovirus multiple times throughout your life because there are many different strains of the virus. Immunity to one strain does not necessarily protect you from others.
While some protection against specific types of norovirus may develop after infection, it is unclear how long this immunity lasts. This may explain why norovirus outbreaks affect people of all ages.
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
Norovirus can make you feel very sick, with frequent vomiting and diarrhea throughout the day. This can result in dehydration (loss of fluids), particularly in young children, older adults, and those with other health conditions. 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
To avoid getting norovirus, do not eat raw or undercooked shellfish.
Annual Illnesses and Outcomes
Each year in the United States, norovirus leads to:
900 deaths, primarily among adults aged 65 and older
109,000 hospitalizations
465,000 emergency department visits, mostly in young children
2.27 million outpatient clinic visits, predominantly in young children
19 to 21 million cases of illness
Economic Impact
Foodborne norovirus illness costs approximately $2 billion annually in the U.S., mainly due to healthcare expenses and lost productivity.
Who Is Most Affected
Nearly 1 million pediatric medical visits occur annually due to norovirus.
Groups more likely to seek medical care include:
By age 5, the following risks are observed:
1 in 110,000 will die from norovirus
1 in 160 will be hospitalized
1 in 40 will visit the emergency department
1 in 7 will visit an outpatient clinic
U.S. Outbreaks
Approximately 2,500 norovirus outbreaks are reported annually in the U.S.
Outbreaks are most common from November to April.
New strains can cause 50% more illnesses during outbreaks.
Outbreaks generally spread through direct contact, like sharing food or utensils.
Global Impact of Norovirus
Norovirus causes about 1 in 5 cases of acute gastroenteritis worldwide, leading to vomiting and diarrhea.
Each year, norovirus contributes to:
Global Outbreak Trends
Norovirus is the leading cause of gastroenteritis outbreaks worldwide.
Outbreaks are most frequent in the winter months (November to April) in northern hemisphere countries and May to September in southern hemisphere countries.
GII.4 viruses have dominated outbreaks since 2002, with some newer strains, like GII.17 and GII.2, temporarily replacing GII.4 in certain regions.
The GII.4 Sydney strain has been the dominant global strain since 2012, often leading to increased outbreaks when new variants emerge.
Norovirus can infect anyone, and people of all ages are susceptible during outbreaks. Your genetic makeup may also influence your likelihood of contracting the virus.
Consuming raw shellfish, such as oysters, can expose you to norovirus, as these filter-feeding shellfish may harbor harmful viruses and bacteria. Children under 5, older adults, and individuals with weakened immune systems are at higher risk of developing severe infections from norovirus.
Cause
Norovirus is spread when tiny particles of feces (poop) or vomit from an infected person accidentally enter your mouth. Even if you can’t see them, billions of norovirus particles are shed when you’re infected, and just a few of these particles are enough to make you or others sick.
How It Spreads
Norovirus is highly contagious and spreads quickly through several routes:
Contaminated Food
A person with norovirus touches food with their bare hands.
Food is placed on surfaces contaminated with feces or vomit particles.
Vomit droplets from an infected person land on food.
Food is grown with contaminated water, such as oysters, or vegetables are irrigated with contaminated water.
Contaminated Water
Drinking or recreational water can become contaminated if a septic tank leaks into a well or if someone with norovirus vomits or defecates in the water.
Water can also be contaminated when it is inadequately treated (such as insufficient chlorine levels).
Contaminated Surfaces
Norovirus spreads when an infected person touches surfaces with bare hands or contaminates objects with norovirus.
Vomit droplets can land on surfaces or be inhaled by others.
Diarrhea from an infected person may splash onto surfaces.
When You’re Contagious
You are most contagious:
When experiencing symptoms, especially vomiting.
During the first few days after feeling better.
However, studies show you can still spread norovirus for up to 2 weeks or more after symptoms subside.
Key Points
Norovirus is highly contagious, but taking simple steps can help prevent its spread:
Wash hands thoroughly with soap and water—hand sanitizer alone is not effective against norovirus.
Avoid handling food or caring for others when you’re sick.
Clean surfaces and items that may be contaminated.
How Norovirus Spreads
Norovirus can be found in vomit and feces, even before you begin feeling sick. It can stay in your system for up to 2 weeks after recovery, and you can still spread the virus during that time.
If You Are Sick
Handwashing
Handling and Preparing Food
Wash fruits and vegetables thoroughly before eating or preparing them.
Cook shellfish, such as oysters, thoroughly—to at least 145°F—to kill the virus.
Keep raw shellfish separate from ready-to-eat foods in the grocery cart, refrigerator, and on cutting boards.
Regularly clean and sanitize kitchen surfaces and utensils, especially after handling shellfish.
Note: Norovirus can survive temperatures as high as 145°F and quick steaming processes may not be enough to kill the virus.
Cleaning and Disinfecting Surfaces
After vomiting or diarrhea, immediately clean and disinfect the area.
Washing Laundry
Immediately wash clothes or linens that may have been contaminated.
By following these prevention strategies, you can reduce the risk of contracting or spreading norovirus.
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