Cases of norovirus — the stomach bug behind what’s sometimes called the “winter vomiting disease” — are already on the rise this holiday season and may hit record numbers, data from the Centers for Disease Control and Prevention (CDC) suggests.
Almost 14 percent of tests for norovirus came back positive over the one-week period ending on November 15, according to the CDC. Over the same one-week period last year, only about 10 percent of tests came back positive, per the CDC.
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The unusually high positive test rates at the start of this norovirus season, which typically runs from November to March, suggest this year might set a new record, says Donald Schaffner, PhD, a professor and the chair of the food science department at Rutgers University.
“Last year was a pretty bad year, and I would say that we are on track to have a similar or worse year,” Dr. Schaffner says.
Norovirus Typically Begins to Peak in December
Norovirus is often called the “winter vomiting disease,” because even though it circulates year-round, cases tend to peak between December and March, says Frank Yiannas, MPH, a former deputy commissioner for food and policy response at the U.S. Food and Drug Administration.
Last year, the positive test rate for norovirus hit a record of nearly 25 percent in December, according to the CDC.
“Seeing activity start to increase in November isn’t unusual,” Yiannas says. But the positive test rate this November is higher than in previous years, suggesting that this year might be worse than in the past, he adds.
“We don’t need to be alarmed, but it’s reasonable to be more vigilant, especially in food-service and institutional environments where norovirus spreads easily,” Yiannis says.
A New Norovirus Variant May Be Causing More Sickness
A new strain of norovirus may be helping drive the recent increase in infection rates.
For years, one strain of norovirus, GII.4, made up the majority of cases, according to the CDC. But a new strain, GII.17, accounted for roughly 75 percent of the outbreaks during the 2024–2025 norovirus season, up from only about 10 percent of outbreaks during the 2022–2023 season.
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“Norovirus does evolve quickly, which means that we have new strains that cause disease,” Schaffner says. The newer GII.17 strain may make more people sick because they generally haven’t been exposed to it before, so they haven’t built up immunity, he notes.
What Are the Symptoms of Norovirus and How Does It Spread?
Norovirus can cause a range of symptoms, including:
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- Nausea
- Vomiting
- Stomach pain or cramps
- Watery or loose diarrhea
- Feeling ill
- Low-grade fever
- Muscle pain
Symptoms usually begin 12 to 48 hours after exposure and last anywhere from 1 to 3 days. People can shed the virus in their stool for several weeks after recovering; those with medical conditions may shed the virus for months.
Norovirus is highly contagious, and can be spread through contact with sick people as well as through contact with contaminated food, water, or surfaces, according to the CDC. People catch norovirus by getting tiny particles of feces or vomit into their mouth from an infected person.
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There are many different ways norovirus can spread from an infected person, per the CDC:
- Contaminated Food Norovirus can spread when an infected person touches food with their bare hands, when tiny particles of vomit or feces get on food preparation surfaces, or when food is grown in or watered with contaminated water.
- Contaminated Water Recreational or drinking water gets contaminated when septic tanks leak into wells, when an infected person vomits or defecates in the water, or when wastewater isn’t treated properly to decontaminate it.
- Contaminated Surfaces An infected person can spread norovirus if vomit sprays through the air and lands in another person’s mouth or on surfaces that another person touches. An infected person may also spread it if they have diarrhea that splatters on surfaces.
What to Do if You Get Sick With Norovirus
There is no cure for norovirus, according to Cleveland Clinic; the infection needs to pass on its own. You can manage symptoms by drinking lots of fluids, getting plenty of rest, and eating soft, bland foods.
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Visit a doctor if you’re unable to eat or drink, Cleveland Clinic notes, or if you have symptoms that last longer than three days.
The best way to avoid spreading norovirus if you’re sick is to avoid preparing or handling food or caring for other people until you’ve been symptom-free for at least 48 hours, according to the CDC.
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Regular handwashing is also key, per the CDC. You should wash your hands for at least 20 seconds with soap and water. This is especially important after using the toilet or changing diapers, before eating or preparing food, and before handling medicine for yourself or someone else.
