Most people in the country right now know someone who is either just getting over or currently enduring a winter vomiting illness.
States like Ohio, Massachusetts and Texas are reporting high or rising levels of “stomach bugs,” which are medically known as many different viruses, including norovirus and gastroenteritis. A Texas middle school even had to close because of high norovirus levels.
These highly contagious gastrointestinal illnesses cause digestive symptoms like vomiting and diarrhea, and tend to pop up more frequently during the cold months.
Here’s what to know about them and how to stay healthy as we make our way through the rest of virus season:
What is norovirus and how is it different from a ‘stomach bug’ or gastroenteritis?
“Norovirus, historically, was called the winter vomiting illness,” said Dr. Stuart Ray, a professor of medicine and infectious diseases at Johns Hopkins Medicine in Maryland. “The peak of norovirus is generally January-February in the Northern Hemisphere, and so we’re just on the tail of the usual peak.”
The hallmark symptoms of the illness include vomiting, nausea, stomach cramps and diarrhea, as well as possible fever and body aches.
Norovirus has been pretty typical for the United States this winter, “so this isn’t an exceedingly bad season, but I think the number of outbreaks we’re hearing about and the disruptions they cause illustrate the impact,” Ray said.
Millions of people get norovirus each year in the U.S., which results in roughly half a million emergency room visits and 1,000 deaths (mostly in older adults), according to Ray.
“I think for many people, this is inconvenient, but not life-threatening,” Ray said. “But people who are very young … and especially people who are old and frail, as well as people with compromised immune systems, this can be a dangerous disease because you can get so dehydrated that you can get into trouble.”
Norovirus is “one of the causes of gastroenteritis,” or a stomach bug, Ray noted. When someone says they have a “stomach bug,” it’s likely that norovirus or something within the umbrella term gastroenteritis is making them sick.
“Gastroenteritis is sort of a catch-all term that refers to an infection or a disorder of the gastrointestinal tract,” said Dr. Daniel R. Kuritzkes, the chief of the division of infectious diseases at Brigham and Women’s Hospital in Boston. “So, anything from the stomach all the way down to the colon.”
Gastroenteritis describes pretty much anything that makes you vomit or gives you diarrhea, Kuritzkes said. Even eating a bad oyster can cause gastroenteritis. Viral gastroenteritis often refers to the collection of vomiting illnesses like norovirus, adenovirus and rotavirus.
These illnesses look really similar, and unlike COVID or the flu, there isn’t a rapid test for norovirus, Ray said. There also isn’t a vaccine or a specific medication for norovirus. Instead, people rely on supportive care like hydration and rest to help them feel better.
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Norovirus, which causes vomiting and diarrhea, generally peaks in January or February but continues to cause illness well into the spring.
Norovirus is commonly spread in close-knit spaces — but not through the air.
“Like other gastrointestinal pathogens, norovirus is transmitted by fecal-oral transmission, and so it’s usually transmitted from somebody who’s ill to other people, often because of poor hand hygiene,” Kuritzkes said.
It spreads when someone comes in contact with contaminated stool or vomit, which could be in food, water or on surfaces.
Norovirus is particularly common in tight-knit community spaces like nursing homes, schools, day cares and long-term-care facilities, Kuritzkes said.
“Some of the most publicized outbreaks are when there’s a norovirus outbreak on a cruise ship,” Kuritzkes explained, like the 76 people who were recently sickened on a Holland America cruise ship. Toward the end of 2025, nearly 100 people were infected on a Royal Caribbean cruise.
In close quarters, the virus can spread as people shake hands, eat food prepared by a sick person or when folks touch contaminated surfaces.
With kids, if they play with a toy and then put their fingers in their mouth, which is all but guaranteed for children under a certain age, they can bring the virus home. Within homes, it can spread if someone with norovirus is preparing dinner, for example, and doesn’t wash their hands well, Kuritzkes noted.
Norovirus doesn’t “hang in the air,” Ray said. Instead, it commonly spreads when someone eats or drinks something that’s contaminated.
If you get sick, you should try to isolate from others.
Sick people should isolate as much as possible, according to Kuritzkes, and shouldn’t prepare food for others.
“The problem is that you shed norovirus for two weeks after the illness,” Ray said. “People can stay infectious for a while when they have no symptoms, and that makes it tough to control these outbreaks.”
“One gram of stool has about 10 billion infectious doses of norovirus,” continued Ray, who added that one gram is the weight of a paperclip. “That means that it’s very hard to clean up norovirus and keep people from getting infected. You really have to be really careful.”
“This is why it shuts down cruise ships … there’s a hospital ward this year that was closed because of norovirus,” Ray noted.
Reinfection is also possible if surfaces aren’t properly decontaminated or if you come into contact with a different strain, which is why proper hygiene and reasonable isolation are so critical.
Keep an eye out for signs of dehydration from vomiting and diarrhea.
Vomiting and diarrhea, the two most common symptoms of norovirus, can lead to dehydration as you’re unable to retain fluids and you’re quickly expelling what’s already in your body.
Signs of dehydration include dry mouth and dizziness when you stand up, Kuritzkes said. Lethargy is also a sign of more severe dehydration, especially in young kids.
The best thing to drink when battling something like norovirus isn’t plain water. Instead, it’s oral rehydration salts, which are available over the counter at the pharmacy, Ray said.
“Things like sports drinks have a lot of the same characteristics,” Ray said. “The key ingredients are salt and sugar, because there’s a special transporter in the gut that works even when you have norovirus, and you can absorb salt and sugar together.” However, oral rehydration salts are ideal because they have the right formula ― sports drinks usually don’t.
Ray added that people should know the alarm symptoms of a winter vomiting illness, which include severe headache, high fever and blood in the stool or vomit. If you notice these things, you should seek medical attention.
Hand sanitizer doesn’t kill norovirus or other stomach bugs.
“Unfortunately, in part because it is a virus that’s gastrointestinal, [norovirus] is designed to be pretty hardy and to be able to survive in the environment, and so it’s harder to destroy,” Kuritzkes explained.
Comparatively, respiratory viruses are pretty fragile and aren’t infectious for long, Kuritzkes added. These can also be destroyed by hand sanitizer — but none of this is true for norovirus or many other viruses within the gastroenteritis umbrella.
If you have diarrhea, or are taking care of a loved one with diarrhea, washing your hands with soap and water is the key to killing the germs ― not hand sanitizer, Ray said.
“Any linens that are soiled need to be washed with soap and water, and be careful about if you handle them, then wash your hands with soap and water after handling those linens,” Ray said.
Even if you can’t see the infected stool, even just one microscopic droplet is enough to be infectious, Ray noted. That’s why it’s doubly important to follow prevention strategies.
