From hantavirus to norovirus: Why cruise ships are a hotbed for deadly disease outbreaks

Cruise vacations are often marketed as luxurious escapes across oceans, offering gourmet meals, entertainment, exotic destinations and all-inclusive comfort.

Yet recent outbreaks aboard multiple ships have once again exposed a darker reality that cruise ships are among the most vulnerable environments for the spread of infectious disease.

In last week alone, two separate outbreaks — a deadly hantavirus cluster aboard the expedition ship MV Hondius and a large norovirus outbreak on the Caribbean Princess — have once again exposed the risks associated with large-scale maritime tourism.

The recent incidents come as international cruise tourism continues to rebound strongly after the Covid-19 pandemic, with Antarctic and expedition cruises witnessing particularly sharp growth in passenger numbers.

Over the years, outbreaks linked to cruise travel have included norovirus, Covid-19, Legionnaires’ disease, E. coli and, more recently, hantavirus.

What happened aboard the MV Hondius cruise ship?

One of the most alarming maritime disease incidents is currently unfolding aboard the Dutch-operated expedition ship MV Hondius, where a hantavirus outbreak left multiple passengers critically ill and led to several deaths.

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The outbreak drew attention across the world because the virus identified was the Andes virus strain of hantavirus — one of the rare hantavirus variants known to spread between humans.

According to the World Health Organisation (WHO), eight individuals connected to the outbreak became ill, including three who died.

At the time the outbreak was first reported on May 2, the ship, operated by Oceanwide Expeditions, carried 147 passengers and crew members onboard, while another 34 individuals had already disembarked earlier during the journey.

The WHO later said four infected individuals remained hospitalised in South Africa, the Netherlands and Switzerland. Another suspected patient transported to Germany ultimately tested negative.

Health officials believe the outbreak likely began before passengers even boarded the vessel. According to the WHO, the first infected individual may have contracted the virus during travel in Argentina or Chile, regions where Andes virus infections have historically been reported.

Investigators believe transmission later continued aboard the ship through close contact among passengers.

The WHO said the risk to the wider global population remained low, although the threat level aboard the vessel itself was considered moderate because of the confined environment and close interactions among passengers.

The outbreak also cast attention on expedition and Antarctic tourism, one of the fastest-growing sectors of the cruise industry.

According to figures from the International Association of Antarctica Tour Operators, the number of tourists visiting Antarctica increased from around 37,000 in 2015 to more than 117,000 in 2025.

More than 80,000 visitors last year participated in excursions that allowed them to step onto land during their trips.

The growing popularity of remote-destination cruises has raised additional questions about onboard medical preparedness, emergency evacuation capabilities and disease surveillance in isolated regions far from advanced healthcare infrastructure.

Why is norovirus still the most common cruise ship illness?

While the hantavirus outbreak generated concern because of its rarity and high fatality rate, norovirus remains by far the most common infectious disease associated with cruise travel globally.

The CDC confirmed on Thursday that more than 100 individuals became sick during a norovirus outbreak aboard the Caribbean Princess, a ship operated by Princess Cruises.

Authorities said the outbreak affected 102 passengers and 13 crew members. Those who fell ill reportedly experienced gastrointestinal symptoms commonly linked to norovirus, including diarrhea and vomiting.

The Caribbean Princess departed Port Everglades in Fort Lauderdale, Florida, on April 28 and was scheduled to return to Florida on Monday. During the voyage, the ship sailed through the Caribbean and was expected to stop in Nassau, the capital of the Bahamas.

According to CruiseMapper tracking data, the vessel was located off the northern coast of the Dominican Republic during part of the outbreak response.

“Princess Cruises can confirm that a limited number of individuals reported mild gastrointestinal illness during the April 28 Caribbean Princess voyage from Port Everglades,” the company said.

The cruise line added, “We quickly disinfected every area of the ship and added extra sanitizing throughout the voyage.”

According to the CDC, the ship carried 3,116 passengers and 1,131 crew members.

Norovirus is extremely contagious and spreads rapidly through contaminated food, water and frequently touched surfaces. The virus can survive for extended periods on objects such as railings, elevator buttons, slot machines, serving spoons and buffet counters.

The Caribbean Princess outbreak was not the only norovirus incident involving Princess Cruises this year. In March, nearly 200 people reportedly fell ill aboard the Star Princess during another outbreak.

CDC data also showed that more than 2,200 people became sick during 18 separate norovirus outbreaks on cruise ships last year.

Despite the headlines generated by cruise outbreaks, the CDC noted that maritime incidents account for only around 1 per cent of all reported norovirus outbreaks in the United States.

The agency estimates that approximately 2,500 norovirus outbreaks occur across the US annually.

Explained: Why do diseases spread so easily on cruise ships?

Public health specialists often describe cruise ships as “semi-enclosed ecosystems” because they combine high population density, continuous social interaction and limited physical separation within a confined environment.

Unlike cities, where people disperse into separate homes and workplaces after daily activities, cruise passengers remain together around the clock for extended periods. Experts say this constant proximity dramatically increases the likelihood of disease transmission once a virus or bacterium is introduced onboard.

Modern mega-cruise ships can carry more than 6,000 passengers along with over 2,000 crew members. In terms of population density, some vessels effectively resemble compact floating cities.

Thousands of passengers may share elevators, dining halls, theatres, casinos, swimming pools, corridors and handrails every day. Such repeated contact creates ideal conditions for infectious agents to spread rapidly.

Experts also point to shared infrastructure systems aboard ships as an additional risk factor. Air circulation has become a major focus of cruise health policy since the Covid-19 pandemic.

Although many modern vessels upgraded filtration systems and increased fresh air exchange after 2020, not all sections of all ships operate under identical conditions. Certain lower-deck areas, crew quarters or older vessels may still depend partly on recirculated air.

Respiratory viruses such as influenza and Covid-19 can spread more easily in enclosed indoor environments where ventilation is limited.

Norovirus outbreaks have repeatedly demonstrated how shared dining systems can become major transmission pathways aboard cruise ships.

Buffets, communal beverage stations and shared utensils can expose hundreds of passengers to contamination within a short period if even one infected person handles food-serving equipment.

Norovirus is especially difficult to eliminate because the virus can remain active on surfaces for days.

Experts note that infected individuals may spread the virus before symptoms appear. A passenger could pass health screenings at embarkation, feel healthy during the first days of the voyage and unknowingly infect others while visiting restaurants, casinos or entertainment venues.

Crew members face particular risks because they often live in tighter quarters than passengers and work across multiple parts of the vessel throughout the day.

Kitchen staff, cleaners, servers and cabin stewards may interact with hundreds of travellers daily.

Public health experts warn that if sick crew members fail to report symptoms — potentially out of concern over lost wages or isolation requirements — they could unintentionally become major transmission sources.

The risk is not limited to gastrointestinal illnesses. Cruise ships have historically experienced outbreaks linked to multiple pathogens, including Legionella bacteria, which can grow inside plumbing systems, hot tubs and decorative water features.

Legionnaires’ disease outbreaks aboard ships have previously forced changes to onboard water management systems.

One notable incident occurred in 1994 aboard the Horizon cruise ship, where contaminated whirlpool spas reportedly infected around 50 passengers.

More recently, smaller outbreaks during 2024 and 2025 were linked to stagnant sections of plumbing systems known as “dead legs,” where water flow is limited and bacteria can multiply.

Health experts are also paying closer attention to measles outbreaks amid falling vaccination rates in some regions.

Although measles cases linked to cruise ships remain relatively uncommon compared to norovirus, specialists warn the virus presents a serious risk because of its extremely high transmissibility.

Measles can remain suspended in the air for hours after an infected person leaves an enclosed space.

In unvaccinated individuals, the disease can cause fever, pneumonia, ear infections and encephalitis, a potentially dangerous inflammation of the brain.

South America and Canada lost their measles elimination status last November.

Public health experts say cruise ships — where travellers from multiple countries gather in crowded indoor settings — could become high-risk environments for transmission if vaccination rates decline further.

What lessons did the Covid-19 pandemic leave behind?

Long before the hantavirus outbreak aboard the MV Hondius or the recent norovirus cases aboard Princess Cruises, the cruise industry had already become a central focus during the global coronavirus crisis.

The Covid-19 outbreak aboard the Diamond Princess in 2020 became one of the most closely studied maritime epidemiology events in modern history precisely because it demonstrated how quickly airborne pathogens could spread onboard.

Out of 3,711 passengers and crew members aboard the Diamond Princess, more than 700 eventually tested positive for the coronavirus, while the ship remained quarantined off Japan.

The incident changed how governments and cruise operators approached maritime quarantines.

Health experts later argued that isolating passengers aboard a ship without hospital-grade ventilation and infection control systems may have worsened transmission in some circumstances.

The crisis ultimately led to major regulatory reforms, including the introduction of stricter health standards, updated sanitation rules and new operational guidelines under programmes such as the CDC’s Vessel Sanitation Program.

The CDC’s Vessel Sanitation Program conducts inspections on ships operating in US waters, with any vessel scoring below 85 considered to have failed inspection standards.

Following the pandemic, cruise companies introduced enhanced sanitation measures, upgraded air filtration systems, revised medical protocols and stricter passenger health screenings.

Despite those improvements, experts say the basic structural realities of cruise ships still make them vulnerable to outbreaks.

Even luxury expedition vessels carrying far fewer passengers than mega-ships remain exposed. A 2019 outbreak aboard the Celebrity Flora in the Galapagos Islands demonstrated that smaller, high-end cruise operations are not immune from infectious disease events.

The industry has also continued monitoring other foodborne illnesses and bacterial outbreaks. In January 2026, health authorities investigated E coli cases linked to the Seven Seas Mariner.

Can cruise ships ever fully eliminate disease risks?

Despite increasingly sophisticated health systems, experts say completely removing disease risks from cruise travel may not be realistic.

Cruise ships operate in an environment where thousands of individuals from different countries and health backgrounds remain in close proximity for extended periods while travelling across international borders.

The rapid turnover between cruises also complicates disinfection efforts. Ships often have only six to 10 hours between voyages to unload passengers, clean cabins and prepare for the next sailing.

Health specialists say that narrow operational window may not always allow for complete deep-cleaning if an outbreak occurs during the previous voyage.

Simply put, when thousands of people share the same elevators, corridors, and handrails, the "basic reproduction number" of any introduced pathogen — the average number of people one sick person infects — skyrockets.

With inputs from agencies