How Cruises Became Modern-Day Plague Ships

Six weeks ago, it would have seemed like the birding adventure of everyone’s dreams. The Dutch cruise ship MV Hondius left Ushuaia, Argentina, on April 1, 2026, with roughly 150 people on board, bound for the islands of the South Atlantic. Among them was couple Leo Schilperood and Mirjam Schilperood-Huisman, seventy- and sixty-nine-year-old Netherlanders who had been travelling for around three months in Chile, Uruguay, and Argentina. The pair were amateur ornithologists; they had published a paper together in 1984 about pink-footed geese. In 2013, they reportedly spotted the Serendib scops owl in Sri Lanka.

While the ship visited South Georgia, on April 6, Leo took ill with gastrointestinal symptoms. He deteriorated and developed respiratory distress before dying on board on April 11. Hondius went on to stop at Tristan da Cunha, Inaccessible Island, Nightingale Island, Gough Island, and Saint Helena—isolated and scarcely populated British Overseas Territories on the Mid-Atlantic Ridge.

Saint Helena, alone among these, has an airport, and here, Leo’s body was brought ashore. Mirjam came ashore too. She had also developed gastrointestinal symptoms. She flew to South Africa, intending to continue home to the Netherlands, but she collapsed in the Johannesburg airport and was admitted to a local ICU. She died shortly thereafter. Thirty other passengers left the ship in Saint Helena. On a subsequent stop at Ascension Island, another passenger, a United Kingdom national, went ashore, having taken ill.

On May 2, UK officials notified the World Health Organization that a cluster of severe respiratory illness had broken out on Hondius, that there had been two deaths, and that another passenger was critically ill. By May 8, six passengers were confirmed to have tested positive for the Andes strain of hantavirus. This strain has been associated with person-to-person spread in the past; it is the only known strain of hantavirus that has demonstrated this ability. It has since been reported that the strain isolated from Hondius, which appears to have spread between passengers and crew, is not significantly mutated.

Hantavirus is distributed around the world and infects about 30,000 people annually. About 3 percent of the global population has serological evidence of previous exposure. It has a natural reservoir among rodents, and human cases are often associated with contact with aerosolized rodent excreta. In North America, hantavirus cardiopulmonary syndrome, its most severe manifestation, is fatal about a third of the time, depending on the strain, timeliness of recognition, and available medical resources. The Andes strain, which is predominant in South America, is one of the more virulent.

Ships—cruise ships especially—have a long and melancholy history of shipboard outbreaks of infectious diseases.

In the early days of the COVID-19 pandemic, in 2020, a SARS-CoV-2 outbreak beset the Diamond Princess, carrying more than 3,700 people, stranding it off the coast of Japan, and denying it free pratique for two weeks. The case demonstrated the extraordinary contagiousness of that virus—with a reproductive number as high as 14.8 (number of people infected in turn by each new case) in the absence of mitigation strategies.

Ships of all shapes and sizes remain crowded spaces, with you-breathe-me, I-breathe-you intimacy, and it has been ships that have seen and been the vectors of some of history’s most frightening instances of contagion. Grain carriers laden with rats and their fleas brought the plague to Constantinople from Egypt in 541, initiating the Plague of Justinian. Procopius’ plague writings are some of the most evocative shit-hitting-fan records; he writes of the ensuing devastation of the Byzantine Empire, describing 5,000 deaths a day in the capital and the near collapse of civil society. The Black Death came to Messina in 1347, prompting the Venetians to institute the policy of quarantine, in which ships were compelled to remain at anchor for forty (quaranta) days before landing.

Grand-Saint-Antoine, a merchant ship, stopped in Marseilles in 1720, having been refused entry at Livorno after several crew, including the chief surgeon, died of suspected plague, after having visited Cyprus. The ship was quarantined, but the isolation was lifted, thought to be the work of an influential local merchant who wanted the cotton and silk on board for a fair.

Epidemics from Yersinia pestis have mostly ceased, with the decline of rat fleas’ once intimate place in our lives and with antibiotics. But on-board outbreaks continue—of norowalk, legionella, and chicken pox, among others—and will, for as long as ship life remains as close as it seems fated to. For the most part, the risks of these are borne by the passengers and crew.

Today, air travel has substantially usurped the role of sea travel for international spread of pandemic pathogens, as was seen during the COVID-19 pandemic, and is by far the greater public health concern. Tarmac delays can never be for forty days in any sane world, and there are only so many terminal hotel beds. And by the time trouble is manifest, it likely will have spread to population centres already.

• The Next Pandemic May Already Be Brewing
• How Alberta Became the Epicentre of Canada’s Measles Outbreak
• Antibiotics May Soon Become Useless

But ships remain excellent vectors of disease. Think of what could happen on Royal Caribbean’s Icon of the Seas, the world’s largest cruise ship, which carries up to 7,600 passengers on twenty decks. It has seven swimming pools, over twenty “ways to dine on board,” and a skating rink. The population of a small town, crammed into its high school. A gastrointestinal or a respiratory virus could get up to a gallop—and very quickly, there would be more people to be cared for than there are carers.

The outbreak on MV Hondius has renewed interest in the matter of cruise ship contagion. Today, these are usually due to gastrointestinal illness (90 percent norovirus), together with familiar respiratory infections, such as influenza and respiratory syncytial virus. The Caribbean Princess was recently in the throes of a 115-person norovirus outbreak; on May 11, it returned to Port Canaveral near Orlando after a cruise through the Caribbean.

Hantavirus is an unusual cause of disease outbreak in any context and is an unprecedented cause of a shipboard outbreak. It has low potential for a pandemic, as it is not really a novel pathogen. The Andes strain of hantavirus has been in contact with humans for a long time, as has hantavirus more generally. This episode will probably come to a close as pathogen spread is contained by demonstrably effective public health measures like those implemented during the COVID-19 pandemic: social isolation, contact tracing, and in time, a vaccine. Phase I studies on Andes hantavirus DNA vaccines have already been published. A phase III trial in suggested safety and efficacy in a formalin-inactivated hantavirus vaccine is available in South Korea and China.

Pathogens will come again, and we will struggle, like we did during the COVID-19 pandemic, during which more than 7 million died. We have filled the planet with 8.2 billion humans. Fuel stacked that tightly burns hot. While media has drawn criticism for ringing the hantavirus alarm bell too hard, it’s worth keeping a close eye on cruise ships whenever these outbreaks occur on board.

In other contexts, public health workers have kept flocks of caged chickens, called “sentinel chickens,” to monitor the presence of arboviruses, such as West Nile Virus. Early in the course of pandemics to come, cruise ships may be epidemiologic tripwires for contagion. Sentinel chickens of the sea.