A hantavirus outbreak on a cruise in the Atlantic has raised questions about the health risks at sea.
The World Health Organization (WHO) has confirmed five cases of hantavirus linked to an outbreak on a cruise ship sailing the South Atlantic, including three deaths.
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Cruises attract millions of passengers every year, often carrying thousands of people for weeks at a time.
While cruise ships are not inherently dangerous, they do create conditions that facilitate the spread of viruses on board, experts say.
“Cruises are sold as floating holidays, but they are also useful for understanding public health,” Vikram Niranjan, assistant professor in public health at the University of Limerick in Ireland, wrote in The Conversation.
He added that, while cruise lines have improved their hygiene and outbreak response systems over time, and many voyages pass without incident, the basic structure of the travel still creates the same challenge.
“Cruise ships are carefully designed places where many people live, eat, relax, and move through the same shared spaces for days at a time. They show how easily illness can spread when people are packed into a single interconnected environment.”
According to the United States Centers for Disease Control and Prevention’s 2026 recommendations for international travel, cruise ship travel presents a unique combination of health concerns.
Travellers from diverse regions brought together in the often crowded, semi-enclosed shipboard environment can facilitate person-to-person, foodborne, and waterborne transmission of communicable diseases, the agency warns.
How common are viral outbreaks on cruises?
The current hantavirus outbreak is the first known outbreak of this type of virus linked to cruise ship travel.
Onboard outbreaks are uncommon relative to the total number of voyages, but when they do occur are often related to gastrointestinal viruses.
The United States’ Vessel Sanitation Program has registered four outbreaks in 2026, two related to norovirus and two from E.coli.
According to the Cruise Lines International Association (CLIA), the world’s largest industry trade association, cases of gastrointestinal illnesses are rare on cruise ships compared to other settings.
While spread on cruises is less common than in schools, daycares, or healthcare facilities, health authorities require cases to be reported.
“Food service plays a big part in this risk. Buffet-style dining, shared utensils, and many people touching the same surfaces can make it easier for stomach bugs to spread,” Niranjan wrote.
“If someone is infected but does not yet feel sick, they may still contaminate food or surfaces before they realise they are unwell,” he added.
One of the most well-known cases of an onboard outbreak occurred aboard the Diamond Princess, when COVID-19 spread through the vessel, affecting over 700 people out of the more than 3,700 passengers and crew.
What happens if you get ill on a cruise?
CLIA’s guidelines for all its members require all ships to have at least one qualified medical professional available 24/7 for medical bay visits or cabin “house calls.”
Cruise ships must also have an examination room, an intensive care room, and equipment for processing laboratory tests, monitoring vital signs, and administering medications.
Patients who require more comprehensive facilities or treatment are typically referred to a shore-side medical facility.
According to Niranjan, the medical facilities available on board are built to provide first aid, basic treatment, and short-term care, not to manage a fast-moving outbreak on a large scale.
“That is why cruise health depends so much on early reporting, quick isolation and strong cleaning practices,” he wrote.
What can you do to limit the risk?
Niranjan recommends preparing for any health-related risk in advance, before boarding the ship.
Keeping vaccines up to date, checking the coverage of travel insurance, and consulting a general practitioner if part of a risk group –such as older adults or pregnant women– are among recommended steps.
Once on board, it is important to be alert to any symptoms.
“If you start to feel unwell, the safest move is to avoid buffets and crowded shared spaces and report symptoms early rather than trying to carry on as normal,” Niranjan wrote.
