New Dominant Norovirus Strain May Be Cause Of Higher Cruise Ship Outbreaks, Cdc Says

Norovirus: Symptoms and prevention of 'stomach flu'

When norovirus cases spike, these are symptoms you should watch out for and measures you can take for prevention.

• Thirteen gastrointestinal illness outbreaks have occurred on cruise ships in 2025, with ten attributed to norovirus.
• This number surpasses pre-pandemic levels and is on track to exceed 2024's total of 18 outbreaks.
• Passengers are advised to practice frequent handwashing, report illnesses promptly, and consider using disinfectants in their cabins.

Pam Feinstein’s cruise was different than usual even before she boarded. Princess Cruises delayed boarding of the September voyage to do a deep-clean of the ship, following cases of gastrointestinal illness on its previous voyage, she said.

When the 75-year-old embarked for a 12-day European cruise with her family, she noticed crew members aboard the Caribbean Princess ship were serving guests at the buffet, for example, and staff carefully wiped down containers or salt, pepper and sugar – which were only available upon request – between each use.

Those measures continued for the first few days. About a day and a half after, she said operations went back to normal. But then, the captain announced there were active cases on board. He advised guests to wash their hands and avoid using public bathrooms, according to Feinstein.

“I'm a little paranoid ... I'll admit,” the Seattle-area resident told USA TODAY. “So it's something always in the back of my mind anytime we get on a ship, regardless. So, you know, having the outbreak was kind of a whole different thing.”

The stricter sanitation protocols returned, along with small tables in front of cabin doors that denoted a quarantined passenger was inside. Even so, she said she “felt pretty good” about their disinfection measures and she and her family did not get sick.

The incident was the first of its kind in a dozen cruises she’s taken with Princess. Princess did not immediately respond to a request for comment.

Gastrointestinal illness has continued to plague cruise ships in recent months. Less than five months into the year, a steady string of norovirus cases has sickened guests and crew members on cruise ships.

There have been 13 outbreaks of gastrointestinal illness on those vessels that met the Centers for Disease Control and Prevention’s threshold for public notification so far in 2025. Most recently, there was an outbreak aboard Viking Polaris, where more than 30 guests and crew reported vomiting and diarrhea. Ten of those 13 outbreaks were caused by norovirus.

For comparison, there were 18 in all of 2024 and 14 the year prior, with norovirus listed as the causative agent in 15 and 13 of those, respectively.

With the CDC's Vessel Sanitation Program (VSP), which inspects cruise ships, impacted by recent staffing cuts at the Department of Health and Human Services, public health officials said they continue to track gastrointestinal illnesses at sea.

Here’s what travelers should know as the industry remains on pace to surpass last year’s total well before this year’s halfway point.

The recent outbreaks represent an increase from before COVID-19 shut down the cruise industry for over a year. There were 10 gastrointestinal outbreaks in 2019, and 11 each in 2018 and 2017, according to CDC records. Norovirus was also the cause in many of those cases.

“While the number of recent cruise ship outbreaks has been higher than in years prior to the pandemic, we do not yet know if this represents a new trend,” the health agency told USA TODAY in an emailed statement. “However, CDC data show a newly dominant strain is currently associated with reported norovirus outbreaks on land. Ships typically follow the pattern of land-based outbreaks, which are higher this norovirus season.”

On land, for comparison, there were 2,407 norovirus outbreaks reported between August 1 and April 9 by the 14 states that participate in the NoroSTAT network, the CDC said on its website, up from 1,230 during the same period in the previous seasonal year.

The agency also found a “possible overreliance on hand sanitizer on ships” during a preliminary review. Those are not as effective against norovirus as washing hands with soap and water, the CDC added in the emailed statement.

Acute gastroenteritis (AGE) incidence rates aboard cruise ships “decreased significantly” from 2006 to 2019 among voyages reviewed, according to a 2021 CDC report, declining from 32.5 cases per 100,000 travel days to 16.9. among guests. For crew members, the figure dropped from 13.5 to 5.2.

“Among passengers, AGE incidence rates increased with increasing ship size and voyage length,” the report stated. “For crew members, rates were significantly higher on extra-large ships (19.8 per 100,000 travel days) compared with small and large ships and on voyages lasting 6–7 days.”

The CDC’s Vessel Sanitation Program will continue, however, as it “is primarily staffed by USPHS commissioned officers who were not subject to the reduction in force,” an agency spokesperson told USA TODAY earlier this month.

With passengers and crew in relatively small, confined areas and often eating together, cruise ships are conducive to the spread of norovirus, according to Dr. David J. Weber, the Charles Addison and Elizabeth Ann Sanders Distinguished Professor of Medicine and Pediatrics at the UNC School of Medicine.

However, only 1% of all norovirus outbreaks reported take place on cruises. “So, most of them are not occurring on cruise ships, but the cruise ships are a perfect setting for it,” Weber, who is also a professor of epidemiology at the UNC Gillings School of Global Public Health, told USA TODAY.

Other common sites include daycare facilities, hospitals and nursing homes.

When an outbreak does occur, cruise lines must activate their prevention and response plans, according to the CDC’s website. The ships take steps to control the outbreak, such as increasing cleaning, isolating sick guests and crew, and notifying others on board about the cases.

The CDC may also request that cruise lines disinfect cruise terminals and delay the embarkation of the ship’s next voyage.

The VSP investigates gastrointestinal outbreaks on ships sailing in the U.S. – or within 15 days of their arrival in the country – in which at least 3% of the guests and crew report being ill. “We may also conduct an outbreak investigation if an unusual gastrointestinal illness pattern or characteristic is found, even if the illness rate is less than 3%,” the CDC’s website reads.

Investigators may board ships to conduct epidemiological and environmental health assessments. “For example, if water is suspected as the source of illness, we give more attention to reviewing places on and off the ship where people could have been exposed to contaminated water,” the CDC said.

The process could also involve collecting samples, such as vomit or stool, to send to a shoreside laboratory to confirm the causative agent.

Cruise Lines International Association, the industry’s leading trade group, said illness on cruise ships is “extremely rare,” and noted that employees follow strict sanitation procedures developed with public health authorities, including the CDC.

“Cruise lines do their part to help ensure a healthy cruise experience and that passengers and crew maintain good hygiene onboard,” the organization said in an email.

The CDC recommends frequent hand washing, particularly before eating and drinking, and after using the bathroom.

If travelers don’t have access to soap and water, Weber said alcohol-based hand sanitizers are “better than doing nothing.” In the event a guest develops symptoms, he recommended they isolate themselves from others and clean their space with a disinfectant. 

Cruise guests should also “promptly” report illness to the ship’s medical staff and follow their guidance, according to the CDC.

As for what appears to be a high outbreak rate this year, Weber also noted that people may be more relaxed about hand hygiene and surface disinfection than during the pandemic, but that it’s ultimately “hard to say.”

“Things go in cycles.”

Nathan Diller is a consumer travel reporter for USA TODAY based in Nashville. You can reach him at ndiller@usatoday.com.