A “newly dominant strain” of norovirus has increased outbreaks of the stomach bug onboard cruise ships, says a US public health agency.
The Centers for Disease Control and Prevention (CDC) told USA Today that a rise in norovirus outbreaks on land could be influencing cases of the illness recorded at sea.
It said: “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.”
Norovirus is a highly contagious stomach bug with common symptoms including diarrhoea, vomiting, nausea and stomach pain.
Of 16 gastrointestinal illness outbreaks recorded by the CDC this year on cruise ships, including e.coli, 12 have been confirmed as norovirus.
An agency review also found a “possible overreliance on hand sanitizer on ships” that is not as effective against norovirus as washing hands with soap and water, reported USA Today.
In 2024, a total of 18 outbreaks were reported by the CDC on cruise ships, the most in over a decade.
Just five months into 2025, norovirus cases causing sickness to passengers and crew members are likely to exceed last year’s figures.
Holland America, Viking Expedition, Seabourn, Cunard, Princess Cruises and Royal Caribbean have each experienced outbreaks of gastrointestinal illness on ships this year.
According to the CDC, each year, there are about 2,500 reported norovirus outbreaks in the US, with cruise ships accounting for just a small number of these.
Measures as part of the CDC's Vessel Sanitation Program (VSP) include increasing cleaning and disinfection procedures, isolating ill passengers and crew and encouraging good hand hygiene in passengers.
It says: “Norovirus can be especially challenging to control on cruise ships because of the close living quarters, shared dining areas, and rapid turnover of passengers. When the ship docks, norovirus can be brought on board in contaminated food or water; or by passengers who were infected while ashore.
“Repeated outbreaks on consecutive cruises may also result from infected crew or environmental contamination. This is because norovirus can persist on surfaces for days or weeks and is resistant to many common disinfectants.”
The Independent has contacted the CDC for comment.
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