Norovirus loves cruise ships. The same was the case with the coronavirus responsible for COVID-19. Crowded rooms, stuffy air, and communal dining on a large boat full of humans create ideal conditions for pathogens to spread. Now hantavirus—a deadly rodent-borne virus that’s usually spread when people breathe in the air-filled feces or other fluids of infected animals—may have figured this out, too: The world now appears to be facing its own fate. First documented shipboard hantavirus outbreak.
Over the weekend, health officials contacted the World Health Organization to report a cluster of deadly illnesses aboard a cruise ship bound for South Africa. Of the approximately 150 passengers and crew on boardthree have died and four have fallen ill—one in critical condition. The ship, MV Hondius, is now anchored off the coast of Cabo Verde, while those on board await further instructions.
The situation is dire and to be honest it’s scary. Currently, officials are struggling to assess the situation. Only two of the seven suspected hantavirus cases have been confirmed by laboratory testing; others are still “suspected,” according to the WHO. And as health officials investigate, more cases may emerge. Hantavirus can simmer in the body for weeks before causing symptoms, and the seven people who have fallen ill so far may have contracted the virus through casual exposure to animals before boarding the ship.
But that is not guaranteed. The possibility remains that hantavirus-infected rats hid on the ship, which could mean more exposure, more illness, and perhaps more deaths. Less likely, but still a real alternative: People could catch the virus from each other, which could pose an additional threat to those on the cruise terminal and beyond — and to the health workers who treat them. At least one type of hantavirus may be capable of transmitting the infection from person to person, in situations involving close and prolonged contact—the kind that cruise ships certainly encourage. And that version, known as the Andes virus, happens to be found in Argentina, from where the ship left a few weeks ago. Researchers are sequencing the virus found on board to confirm its identity, but for now, “our working hypothesis is that it’s an Andean virus,” Maria Van Kerkhove, acting director of epidemic and pandemic control at the WHO, told me via email.
No matter which version of the truth this is, many people are now trapped on a cruise ship, which may contain a deadly virus that is probably being transported by infected rats and/or humans. The virus can kill up to half of the people it infects, so further spread could have dire consequences. At least one person who became ill was removed from the ship and treated at a hospital; further transfers are planned. But most of those on board have no clear indication of when they will be released. Oceanwide Expeditions, the company operating the voyage, said the ship was suffering from a “serious medical condition” and that the company was cooperating with authorities and working to “adhere to strict health and safety procedures.”
Eventually, of course, all the ship’s passengers will have to disembark; Spain has agreed to receive the ship in the Canary Islands. Still, health officials still can’t say how much risk the passengers and crew will pose to the wider global community. All told, this incident is a sobering reminder that cruise ships can be places of infectious disease nightmares—because they provide germs with so many easy opportunities to spread.
The dangers of cruise ships were painfully apparent during the first days of COVID, when the coronavirus passed. hundreds of people aboard Diamond Princess. In many ways, the ships represented – and, indeed, embraced – the realities that epidemic alarmists were warned to avoid: intimate spaces, indoor communal dining, crummy ventilation in public spaces.
The setup also favors norovirus, one of the most common pathogens on cruise ships, said Vikram Niranjan, a public health researcher at the University of Limerick, in Ireland, who written about the dangers of shippinghe told me. Norovirus is highly contagious, and is transmitted when people come into contact with infected feces or vomit. Contaminated food, water, and surfaces are common culprits—easy to find when dealing with shared utensils and restaurant-style dining.
Additionally, the ship’s interior, where passengers from all over the world mingle and breathe in the stale air, is especially friendly to whatever respiratory pathogens make it in—COVID, the flu, and now maybe hantavirus. And with viruses that seem to be able to spread from person to person, long trips that last several weeks, like this one, are ripe for frequent transmission. Suspected hantaviruses began to show symptoms several weeks apart, raising the possibility that the illnesses represent chainrather than a group of cases with the same source. Additionally, one of the people who is ill and will be evacuated soon is reported to be the ship’s doctor, a common contact for confirmed cases.
Van Kerkhove said the WHO team suspects that “there may be many ways in which people are infected – through contamination by rodents but also through human-to-human contact.” The researchers were told the rats were not on the ship, but “I, of course, cannot confirm that,” he added. “If it’s a ship, there’s always a possibility.”
All things considered, “it’s increasingly looking like there’s human-to-human transmission,” Bill Hanage, an epidemiologist at the Harvard School of Public Health, told me. At the same time, Hanage noted, the nature of the cruise ship that could allow such a spread could make it difficult for scientists to prove the possibility. Even on land, human-to-human transmission is very difficult to prove: People who tend to spend a lot of time together are among the most likely to spread disease to each other, but they are also likely to have the same exposure to an outside source. Inside the ship, even strangers are constantly wandering around, widening the net that researchers have to cast.
Neither Niranjan nor Hanage thinks that taking a cruise is a vow not to sail. (To the contrary, Niranjan said: He’d still like to go on a cruise one day.) But realistically, the stakes are as high as they would be for any other full-on, long-term party. If nothing else, pathogens thrive on our love for one another.
