Norovirus refers to a group of approximately 50 virus strains that lead to a particularly unpleasant outcome: frequent bathroom visits. Annually, around 684 million people worldwide are affected by this virus.

This virus is a form of infectious gastroenteritis, which Dr. Ambreen Allana, an infectious disease expert from Texas, describes as “an inflammation of the bowel and colon that can result in diarrhea and vomiting.”

Although norovirus can spread throughout the year, it is often dubbed the “winter vomiting bug” due to its prevalence from December to February in the northern hemisphere. This is according to Dr. Laraine Washer, who is the medical director of infection prevention and epidemiology at the University of Michigan’s medical school.

Here are the key facts you need to know.

How does norovirus spread?

Norovirus is extremely contagious. It usually enters the digestive system through microscopic viral particles from an infected person’s saliva or feces. These particles can transfer to your hands or contaminate food and drink, eventually making their way into your mouth—a process known as the “fecal-oral route,” Washer explains.

The virus particles can remain infectious on hard surfaces, such as doorknobs and bathroom fixtures, for up to two weeks. It requires minimal exposure to become infected. “The infectious dose of noroviruses is fewer than 20 virus particles,” Washer notes. In comparison, COVID-19 requires exposure to between 100 and 400 virus particles for infection. “When someone is actively infected with norovirus, there are billions of virus particles per gram of stool,” Washer adds.

There is also some risk of transmission via aerosolized particles, particularly if you’re around someone while they are experiencing symptoms like diarrhea or vomiting.

Norovirus becomes contagious about two days prior to the onset of symptoms, and people can remain contagious for days or even weeks after they’re feeling better.

Close quarters such as eldercare facilities, daycares and airports are a “perfect nidus for catching infection”, says Allana. Cruise ships are particularly notorious: the CDC has reported 16 norovirus outbreaks on ships stopping in US ports in 2025 alone.

What are the symptoms of norovirus?

The onset of norovirus symptoms can feel sudden, starting with abdominal cramping, sweating, chills, nausea, vomiting and “very watery diarrhea”, says Washer. Most cases are “mild” in the medical sense, meaning they resolve within three days.

Nonetheless, it’s an extremely unpleasant illness. “People can feel pretty wiped out, fatigued; they may have a low-grade fever, headache. And in most cases, individuals are not able to continue doing their normal activities,” says Washer.

Do I need medical care for norovirus?

Each year, norovirus causes 570-800 deaths and 70,000 hospitalizations in the US, with people over 65 at greatest risk. Those most likely to have severe norovirus are “children less than five years of age, and especially older individuals and those who are immunocompromised”, says Washer.

Those in higher-risk age categories are also particularly susceptible to kidney injury due to dehydration from excessive diarrhea, says Allana. If you or a family member is in a higher-risk age category and unable to keep down liquids, Allana recommends seeing your doctor or going to your local emergency department to receive IV fluids.

Most adults and older children without underlying conditions recover from norovirus without medical intervention. While the CDC reports 2,500 norovirus outbreaks annually in the United States, the actual number of infections is closer to 21m – most cases go unreported because people can “deal with their infections at home”, says Washer.

While there’s nothing you can do to shorten the duration of a bout of norovirus, it’s important to stay hydrated throughout. “Try drinking the same amount of Gatorade or water as the volume that comes out,” says Allana. “Ice chips, ice lollies – really anything you can keep down that will keep you hydrated.”

An antiemetic – medication that prevents nausea and vomiting – like Dramamine may be necessary if you can’t keep liquids down. Do not, however, take medicines that stop diarrhea, like Imodium or Pepto-Bismol, says Washer. “Our body is trying to get rid of the infection, and if we keep the viruses inside … they stick around for longer periods of time,” she says.

How can you avoid getting norovirus?

We don’t have a norovirus vaccine yet. That’s because norovirus is “incredibly difficult” to grow and study in labs, says Dr Andrea Love, an immunologist and microbiologist who has written about norovirus on her Substack. The virus has many different strains, which mutate frequently, making broad protection challenging, Love explains.

That leaves the basics.

Wash your hands: “To prevent or control outbreaks, good handwashing is important for everyone,” advises a representative from the CDC via email. “Importantly, infected individuals should not prepare or handle food, or care for others when they are sick.”

Hand sanitizer and other alcohol-based disinfectants do not work against norovirus, because of how the virus is structured. “You can use hand sanitizers in addition to handwashing, but hand sanitizer alone does not work well against norovirus and is not a substitute for handwashing,” according to the CDC spokesperson.

Wash your hands frequently and thoroughly, with good-quality soap, for at least 20 seconds, says Allana.

Avoid using an infected person’s bathroom: If possible, designate a separate bathroom for the sick person in your household until they recover, and limit other contact, Washer suggests.

Clean affected items: Clean surfaces with diluted bleach (1 cup per gallon of water) or undiluted 3% hydrogen peroxide, both of which can kill norovirus. Wear disposable gloves when cleaning a bathroom where someone has been sick, and take reasonable precautions when working with strong chemicals, says Washer.

When travelling, such as on an airplane, use a paper towel when touching surfaces like the washroom tap and door handle.

Strong chemical agents are required to kill norovirus, and most disinfecting wipes don’t do the trick. But you may be able to find specialized bleach wipes at medical supply stores. Wear protective gloves while using them, and leave them on any contaminated surface for a few minutes.

As for laundry, wash and dry contaminated items separately on hot (norovirus can survive temperatures up to 158F or 70C), with bleach if possible. Running a bleach cycle of the washer in between loads won’t hurt.

Avoid communal dining: Take extra steps to limit exposure. Buffets and potlucks pose particular risks, since multiple people handle serving utensils, and food comes from different kitchens. “If you really want to decrease your risk, avoiding potlucks around this time of year might be helpful,” Washer says.

If you do get norovirus, continue taking precautions after recovery, and don’t assume immunity will protect you for long. “We don’t develop robust memory immunity to norovirus,” says Love. “People can become infected by norovirus every few months because of that.”