As winter takes hold, bringing with it an uptick in respiratory illnesses such as influenza and respiratory syncytial virus (RSV), another highly contagious pathogen is making its seasonal resurgence—norovirus.
Often referred to as the “stomach flu,” norovirus is not related to influenza but is a leading cause of acute gastroenteritis, leading to severe gastrointestinal distress, including vomiting and diarrhea.
Recent data from the Centers for Disease Control and Prevention (CDC) indicate that norovirus outbreaks in the United States are on the rise this winter, surpassing previous years’ numbers. Experts are concerned that this surge could be worse than previous seasons, impacting healthcare systems, schools, restaurants, and even cruise ships.
A Surge in Norovirus Cases Across the U.S.
Tracking data from 14 states show that norovirus outbreaks are becoming more widespread. In early December 2024, the CDC recorded 91 outbreaks, which is more than double the highest average reported during the same week over the past three years. The numbers also represent a sharp increase from the 69 outbreaks reported just the previous week.
Other monitoring tools tracking norovirus positivity rates reveal a growing trend. For the week ending December 28, more than 22 percent of norovirus tests came back positive—almost twice the 12 percent positivity rate recorded for the same period in 2023.
Several states have reported significant spikes in norovirus cases:
- Minnesota documented over 40 outbreaks in December—nearly twice the usual number.
- West Virginia saw a 65 percent increase in norovirus cases from November to December 2024, nearly doubling the state’s average for this time of year.
- Colorado has also reported an above-average number of norovirus outbreaks.
Erica Constance Prochaska, MD, a pediatric infectious diseases specialist at Johns Hopkins Children’s Center in Baltimore, has seen firsthand the increase in cases.
“We’re seeing a ton of vomiting and diarrhea right now because of norovirus,” says Dr. Prochaska. “This stomach virus typically becomes more common during the winter months when people are inside and close to each other, and we’re seeing it surge more now compared to other years.”
How Norovirus Spreads: A Persistent Threat
Norovirus spreads incredibly easily and is primarily transmitted through contaminated food and water. The virus is a leading cause of foodborne illness in the United States, responsible for over half of all reported cases of food-related sickness.
One of the most concerning aspects of norovirus transmission is that infected individuals can shed billions of viral particles in their vomit and feces, and it only takes a few particles to infect another person.
Additionally, new research suggests norovirus may also spread through airborne droplets when an infected person vomits, further increasing the ease with which the virus moves through communities.
Food and Norovirus: A Risky Combination
Uncooked or improperly handled food can be a significant source of norovirus infection. The U.S. Food and Drug Administration (FDA) recently issued a warning about norovirus-contaminated oysters from Washington state, emphasizing the risks associated with raw shellfish.
Other common culprits in norovirus outbreaks include:
- Leafy greens
- Fresh fruits
- Shellfish such as clams, geoducks, mussels, and scallops
Food service workers are a frequent point of transmission, as they handle food, utensils, and surfaces that can easily spread the virus. If a worker carrying norovirus fails to wash their hands properly, they can unknowingly contaminate ready-to-eat foods, leading to widespread outbreaks.
Dean Winslow, MD, an infectious disease specialist at Stanford University, warns about the virus’s ability to persist in public spaces.
“Norovirus can persist for fairly long times on inanimate surfaces like a stair railing, doorknobs, and other objects like that,” says Winslow.
High-Risk Environments for Norovirus Outbreaks
While norovirus can infect anyone, anywhere, certain locations are particularly vulnerable due to their high concentration of people and shared spaces.
1. Restaurants and Catered Events
Given that contaminated food is a major source of norovirus outbreaks, restaurants, cafeterias, and catered events are among the most frequent settings for mass infections. A single sick food handler can transmit the virus to dozens or even hundreds of people in a matter of hours.
2. Schools, Childcare Centers, and Healthcare Facilities
Because young children and the elderly are especially vulnerable to the virus, schools, daycare centers, and nursing homes frequently experience norovirus outbreaks. These environments involve close contact, shared surfaces, and challenges in maintaining strict hygiene standards, making them ideal conditions for the virus to spread.
3. Cruise Ships: A Norovirus Hotspot
Cruise ships have long been associated with norovirus outbreaks, leading some to joke that the illness gives new meaning to the phrase “poop deck.”
In early January 2025, a Holland America cruise ship reported that at least 86 passengers fell ill due to norovirus. This outbreak was one of more than a dozen norovirus incidents reported aboard cruise ships in 2024.
Dr. Winslow attributes the recent rise in cases to increased travel and social interaction following the COVID-19 pandemic.
“People are back out there living their lives, going to bars, restaurants, and on cruises, and this may be a factor in the spread of norovirus,” he says.
Recognizing Norovirus Symptoms
Norovirus symptoms can strike suddenly and severely. The most common signs of infection include:
- Nausea and vomiting
- Diarrhea
- Stomach pain
- Fever
- Body aches
Dr. Winslow notes that norovirus is particularly notable for causing extreme nausea and vomiting in the first 24 hours of illness.
“Compared to many of the other viruses that cause gastrointestinal infections, norovirus causes prominent nausea and vomiting during the first day of illness — even more prominent than the diarrhea,” he explains.
The illness typically lasts between one and three days, and most people recover with rest and proper hydration. However, for certain populations, norovirus can be more serious.
Each year, norovirus is responsible for:
- 465,000 emergency department visits (mostly in young children)
- 900 deaths (primarily among adults 65 and older)
Preventing the Spread of Norovirus
While there is no vaccine for norovirus, the CDC offers several recommendations to help prevent transmission:
1. Wash Your Hands Properly – Using soap and water for at least 20 seconds is the best way to remove norovirus from your hands. Hand sanitizers are not as effective against the virus.
“The virus does not wash off of hands with sanitizer very well — it really requires a good scrub with soap and water,” says Dr. Prochaska.
2. Avoid Preparing Food if You’re Sick – If you have norovirus symptoms, you should avoid handling food or caring for others until at least 48 hours after symptoms disappear. However, research suggests that individuals can still spread the virus for up to two weeks after feeling better.
3. Disinfect Surfaces and Wash Contaminated Clothes – Norovirus can survive on hard surfaces for up to 12 hours and on carpets for up to 12 days. Regular disinfection and laundering of contaminated clothing can help reduce transmission.
Looking Ahead: When Will the Surge End?
Dr. Prochaska warns that norovirus cases may continue to rise in the coming weeks.
“I think we’re still in the thick of things,” she says. “We typically see a lot of transmission through the colder months, and then things let up in the early to mid-spring.”
Until then, health officials urge the public to remain vigilant, practice good hygiene, and take extra precautions to prevent the spread of this highly contagious virus.