A highly contagious new strain of norovirus could be behind soaring cases of the vomiting bug on cruise ships, scientists have warned.
There have been 13 cases of gastrointestinal illness outbreaks on cruise ships so far in 2025, with ten of these attributed to norovirus, meaning the number is well on track to exceed the total of 18 recorded in the whole of last year. It’s already higher than the typical annual average for the pre-pandemic period, leaving health experts puzzled as to what might be behind the uptick in cruise ship illness. The US Centers for Disease Control and Prevention (CDC) now believe that the emergence of a new form of the virus may be allowing it to spread more easily.
It follows a winter of higher-than-usual norovirus cases in the US as a whole.
A similar pattern has been observed back in the UK, with NHS England finding that recorded cases in hospital were 30% higher than the same period last year during the peak of infections in January.
Commenting on the high number of cases on cruise ships, a CDC spokesperson told USA Today: “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.
“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.”
Cruise ships make a perfect environment for norovirus outbreaks due to their close-quarter layout, where passengers and crew are in constant contact, facilitating rapid spread.
Shared dining areas, buffets, and recreational spaces also provide many opportunities for the virus to transmit via contaminated surfaces or food.
Once the virus is introduced to a ship, it can quickly affect a large proportion of those on board – meaning outbreaks can spread rapidly, and become difficult to avoid.
Earlier this month, a luxury cruise ship returned to the UK after experiencing hundreds of norovirus cases.
Over 200 passengers and 17 crew members were struck down with the illness during the 29-day voyage of the Cunard Line’s Queen Mary 2.
The ship had left Southampton on March 8 to follow a route through Caribbean ports and New York City – but as the journey went on more passengers reported experiencing gastric illness, forcing the ship to impose quarantine measures and stool testing on affected people.
The CDC said that Cunard Line had also increased cleaning and disinfection on board after the outbreak was confirmed.
Symptoms of norovirus typically display around 12 to 48 hours after exposure, and include diarrhoea, vomiting, nausea and stomach pain, alongside a fever, headache and body aches.
Most people recover from norovirus within one to three days, though this can be longer for people with weakened immune systems.
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