Norovirus Outbreaks Common on Land and While at Sea

With twelve norovirus outbreaks already confirmed in 2025, the cruise ship industry is on pace to set an unfortunate record without the availability of a preventive vaccine.

Last year, 18 norovirus outbreaks were confirmed on U.S.-based cruises. 

According to a U.S. CDC Emerging Infectious Disease report (Volume 31, Number 4—April 2025), foodborne pathogens, led by norovirus, have impacted people's health for years.

On March 19, 2025, the CDC estimated the number of illnesses, hospitalizations, and deaths in the U.S. caused by seven major foodborne pathogens: Campylobacter spp., Clostridium perfringens, invasive Listeria monocytogenes, nontyphoidal Salmonella serotypes, atoxin-producing Escherichia c,oli and norovirus.

These pathogens caused about 9.9 million domestically acquired foodborne illnesses in 2019. Together with Toxoplasma gondii, these pathogens caused 53,300 hospitalizations and 931 deaths.

Each year, about 2,500 norovirus outbreaks occur in the U.S.

Specifically, the CDC writes, 'Norovirus caused most illnesses, about 5.5 million illnesses, and 22,400 hospitalizations, according to this analysis.'

'When considered with other information, such as major food sources of illnesses, population groups affected, and costs of making foods safer, the estimates can be used to prioritize food safety interventions.'

Regarding cruise ship norovirus outbreaks, a study published in January 2025 supports the CDC's conclusion.

A University of Surrey–led research team identified cruise ship dining areas as priorities for preventing disease outbreaks such as norovirus.

This study, published by Science of the Total Environment (Volume 962, January 25, 2025, 178286), measured CO2 concentrations, RH, and temperature levels on cruise ships while at sea. 

Ventilation performance was assessed in nine spaces on a sailing cruise ship.

These researchers found that nightclubs and theaters are over-ventilated, while pubs and restaurants require increased ventilation.

The good news is that the probability of airborne infection in a speaking normal condition is low (<3 %).

This study's conclusion indicates that dining on cruise ship decks in the open air may be advisable to avoid a norovirus incident.

Visit this webpage to learn more about outbreaks of gastrointestinal illness on cruise ships in the CDC's Vessel Sanitation Program, including outbreak details and actions taken in response.

 As of March 24, 2025, preventive vaccines targeting Human norovirus disease are in demand.

However, developing a broadly effective vaccine in 2025 remains challenging owing to the vast genetic and antigenic diversity of noroviruses, which have multiple co-circulating variants of different genotypes.

Several norovirus vaccine candidates and therapies are being conducted in clinical research this year.