Norovirus is spreading earlier again this year

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A nasty, highly contagious virus is spreading across the country ahead of the holiday season — and it’s not the flu or Covid.

Norovirus, also called the “winter vomiting disease,” has been rising across the nation since as early as mid-October, especially in states like Louisiana, Michigan and Indiana, according to data from WastewaterSCAN, an academic program through Stanford University in partnership with Emory University.

With data through Nov. 21, Amanda Bidwell, scientific program manager for the WastewaterSCAN program, said norovirus wastewater concentrations have increased nationwide by 69% since October.

“Right now, we’re in the high category for norovirus at the national level,” she said. Rates are high in the Northeast and Midwest region, according to wastewater data.

Rates are currently lower compared to last year’s spike, which was overwhelmingly caused by the variant GII.17, which may have mutated to become more contagious, experts said. Between August and November 2024, there were 235 reported norovirus outbreaks, according to the Centers for Disease Control and Prevention.

There have been 153 outbreaks during the same time period this year.

It’s unclear whether the same level of illnesses will continue into 2026, but outbreaks are expected to keep rising, Bidwell said.

“We have three years of data to kind of show that we have this strong seasonal pattern,” she said. “But I can’t say right now how big of a peak it will be.”

A CDC spokesperson said the agency is closely monitoring the norovirus season, which is most common from November to April.

The CDC tracks norovirus through voluntary reporting from clinical laboratories and health departments, but doesn’t currently monitor for norovirus through wastewater, which may be a reason its tracking doesn’t match the WastewaterScan data. People may be sick, but not go to the doctor.

Bidwell said wastewater is an “unbiased way of looking at what is happening in a community.”

Here’s what to know about norovirus and its spread this year.

Norovirus variant becoming more dominant
For over 30 years, norovirus outbreaks have been dominated by one strain, GII.4. Last year’s outbreaks were overwhelmingly caused by the variant GII.17, making up around 75% of outbreaks.

The GII.17 strain has become more prevalent in several countries, including the United States, through the 2020s. The rise of GII.17 may explain why the 2024 spikes and this year’s spread started earlier in October, instead of winter.

Dr. Robert Atmar, professor in the Department of Medicine at Baylor College of Medicine, said a combination of factors may have led to GII.17’s dominance.

“The two possibilities is that something in the virus changed to make it more transmissible, or there were changes in the population that a larger proportion were susceptible,” he said. “And probably it’s a combination of both. But whether it’s going to persist this year, I think, is one of the big questions in our scientific community.”

Dr. Craig Wilen, associate professor of laboratory medicine and immunobiology at Yale University, said GII.17 may not actually be more transmissible, but many people probably have less immunity to the new variant.

“Probably the GII.17 last year was so effective at infecting so many people because we had significantly less immunity to that virus, since it was different enough from viruses that we’ve previously been infected with.”

It’s difficult to say how this year’s norovirus season will turn out.

Atmar said either variant has a “50/50 chance” of dominating this year, but doesn’t expect the same level of illnesses as last year because of “increased immunity.”

Norovirus symptoms
Norovirus is a highly contagious, human-only disease. Norovirus outbreaks can happen anywhere and cause around 20 million infections a year. It’s responsible for over half of foodborne illnesses in the U.S. each year.

It spreads from person to person through vomit or feces drops that end up in peoples’ mouths. It can also spread through coming in contact with contaminated food, water or surfaces.

The main symptoms are diarrhea and vomiting, earning it the name “two-bucket disease.” Other symptoms include fever, stomach pain and body aches.

Symptoms like vomiting and diarrhea may require medical attention for older adults, young children and people with weakened immune systems, according to the Mayo Clinic.

Symptoms usually start within 12 to 48 hours after exposure and last for a few days. Someone can still spread the virus for more than two weeks, even after symptoms are gone.

How to protect against norovirus
Norovirus is notoriously difficult to kill. It’s difficult to wash away and can survive temperatures up to 145°F. Many scientists call it the “perfect pathogen.”

Wilen said norovirus is “highly stable in the environment.”

“It’s highly infectious. Traditional ethanol-based hand sanitizers don’t work as well for this virus as they do for other viruses,” the Yale associate professor said.

In order to kill norovirus, the CDC recommends washing your hands vigorously with soap, cleaning infected areas with diluted bleach and washing infected clothes with hot water and detergent. Wearing gloves and throwing them out after cleaning adds protection.

Fruits and vegetables should be properly cleaned, and oysters and shellfish are properly cooked can also reduce infection risk, the CDC says.

There isn’t a specific treatment for norovirus, but rehydration is key to replace lost fluids.

Though there’s currently no vaccine for norovirus, a Phase 3 Moderna trial is in place.

I don't trust vaccines though. Ever since I had the covid jabs all I've been hearing is horror stories that they're causing cancer and heart attacks.

I have lost count of how many COVID boosters I have had and I am fine.

I've had three, but no more. I'm too put off now by all the conspiracy theories that are springing up, ones that didn't exist before I had the vaccines. Many say the vaccines were rushed and contain poison that could be lethal in some people at random.

But I'd rather die than be sick.

I would have the norovirus vaccine when it's ready, but I don't want a side effect to be vomiting, like a side effect to the covid vaccines were flu-like symptoms.

I hate, hate, hate vomiting.

Unfortunately, outbreaks of norovirus are on the rise. According to WastewaterSCAN, which monitors diseases through municipal wastewater systems, norovirus levels are “high” nationally.

Norovirus concentrations are up 45% since November, and there's been a significant upward trend in the last 3 weeks, Marlene Wolfe, Ph.D., professor at Emory University and program director at WastewaterSCAN, tells TODAY.com. Levels are currently the highest in the Midwest and Northeast.

Two schools in Massachusetts closed for several days this month due to suspected norovirus outbreaks after dozens of students were absent with stomach bug symptoms, NBC Boston reported.

Norovirus outbreaks are also surging on cruise ships.

Norovirus Surge
“We’re seeing upticks in norovirus across the system, but that’s not out of the ordinary. ... It's historically a winter bug," Dr. Scott Roberts, assistant professor of infectious diseases at the Yale School of Medicine, tells TODAY.com.

Currently, outbreaks are rising. Between Aug. 1 and Dec. 11, there were 268 norovirus outbreaks reported by the 14 states participating in the CDC’s NoroSTAT program.

However, WastewaterScan data show a clear early surge. “The concentration really started increasing around October,” says Wolfe.

Although cases are rising, the number of outbreaks at this point in the season is lower than it was last year and within the average range for this time of year, per the CDC.

“So far, we’re not yet to the level that we were at last year, which was really our worst year since pre-COVID ... but it’s certainly going up," says Roberts.

Norovirus GII.17 Variant
Since the early 2000s, the majority of norovirus outbreaks have been caused by one strain, GII.4, NBC News reported previously.

About 10 years ago, a variant called GII.17 emerged in Asia and has taken off in recent years. During the 2024-2025 season, GII.17 caused 75% of norovirus outbreaks in the U.S., compared to less than 10% in 2023, according to a study from the CDC.

“Whenever there is a new strain, it’s really easy for it to start spreading rapidly, and that’s what we saw last year,” says Roberts.

It's unclear whether GII.17 is more transmissible than GII.4, the experts note, but it's possible that more people are susceptible to infection because they don't have immunity.

Norovirus Symptoms
"It's really not subtle infection," says Roberts. Norovirus often begins suddenly, within 12–48 hours after being exposed.

"Fortunately, it's relatively brief. You’re miserable for about 48 hours, then you get better,” says Schaffner. Norovirus usually goes away on its own after one to three days.

However, norovirus can lead to fluid loss and dehydration, the experts warn. Some people are at higher risk for severe disease, complications and hospitalization, says Schaffner. These include children under the age of 5 and adults over 85.

Seek medical care if your symptoms persist after a few days, there's blood in your stool or vomit, or you have signs of dehydration such as dark urine or dizziness, per the Cleveland Clinic.

Norovirus Treatment
There is no specific treatment for norovirus, but symptoms can be managed with supportive care like rest and replenishing fluids, says Roberts. Sports drinks can help restore electrolyte levels.

"Don’t try to drink a lot all at once because it can come right back up," says Schaffner.

What Kills Norovirus on Surfaces?
The most effective household cleaner to kill norovirus is bleach, such as bleach wipes or bleach-based disinfectants, experts previously told TODAY.com. Norovirus isn't susceptible to alcohol-based cleaning products.

Does Hand Sanitizer Kill Norovirus?
Norovirus is very hard to kill. Alcohol-based sanitizers and cleaners are not effective against norovirus because the virus particles have a firm outer shell that alcohol won't break down, the experts note.

Instead, the virus needs to be physically washed off the hands. "You have to use soap and water, which literally picks up the virus and washes it down the drain," says Schaffner.

Bleach-based cleaners are effective at killing norovirus on surfaces and objects.

How to Prevent Norovirus
It isn’t always possible to avoid norovirus — sometimes, it's just bad luck. However, you can take steps to lower your risk of getting norovirus and spreading the infection to others.

Wash your hands frequently, especially after using the bathroom and before eating.
Disinfect contaminated surfaces and objects with bleach.

Avoid direct contact with infected people.

If infected, isolate for at least 48 hours.

Avoid cooking for others when sick.

Cook shellfish to at least 145 degrees Fahrenheit.

If you have questions or concerns, talk to your doctor