Tourism Unusually high number of norovirus outbreaks on cruise ships
There have been an unusually high number of norovirus outbreaks on cruise ships in the first few months of the year. Almost as many outbreaks have been reported to the US health authorities this year as in the entire previous year.
06.07.2025, 06:47
SDA
According to the Vessel Sanitation Program of the US health authority CDC, 12 outbreaks have already been recorded this year (as of 14.5.). In 2024, 15 outbreaks of gastrointestinal illnesses were recorded in which norovirus was proven to be the cause, compared to 13 in the previous year. In previous years, the figures were even lower - if only because of the restrictions in the pandemic years.
Experts say that one possible reason for the high number is that the population's basic immunity to a relatively new norovirus variant is still low. In the USA in particular, there have been a large number of norovirus infections recently. Regionally, the number of outbreaks from August 2024 to the beginning of June 2025 was almost twice as high as in the same period before.
A cruise ship outbreak appears in the CDC data when three percent or more of the ship's passengers and crew showed symptoms.
Cruise ships offer ideal conditions
Noroviruses are spread worldwide and are one of the most common triggers of acute gastrointestinal illnesses in humans. Typical symptoms are the sudden onset of severe vomiting and diarrhea, accompanied by nausea, abdominal pain, headaches and general weakness. The disease can lead to dangerous dehydration, especially in children and the elderly.
The pathogen is highly contagious; a person can become infected with just a few virus particles. An approved vaccine against noroviruses does not yet exist. The norovirus has long been associated with cruises: cruise ships offer ideal conditions for the spread of the virus through the daily use of communal facilities by thousands of people.
Outbreak can build up quickly
According to experts, one norovirus patient on board, one contaminated object or one contaminated food item can be enough to trigger an outbreak. The virus has an extremely short incubation period, which means that there can be a large number of waves of infection during a cruise and events can really build up. There have also been outbreaks on the same ship over several cruises.
According to CDC data, for example, there was an outbreak on the Queen Mary 2 in March, with 266 of the 2538 passengers recorded as being ill.
