In the span of a few weeks, an expedition cruise from Argentina toward Cape Verde
turned from an exclusive wildlife voyage into an international public health emergency after the MV Hondius became linked to an outbreak of hantavirus.The MV Hondius, operated by Oceanwide Expeditions, was sailing through the frigid waters of the South Atlantic on what the company called its “Atlantic Odyssey” voyage. The expedition began in Ushuaia, Argentina, and was designed to carry passengers across remote islands, including South Georgia, Tristan da Cunha and eventually toward Cape Verde, bridging the gap between the Antarctic and Arctic cruise seasons.
The voyage attracted wildlife enthusiasts, birdwatchers and adventure travelers, as passengers were offered opportunities to see penguins, fur seals, albatrosses, dolphins and humpback whales during a six-week expedition at sea.
The World Health Organization had reported eight confirmed or suspected cases, including three deaths, among passengers linked to the voyage. The outbreak challenges assumptions about disease transmission, exposes vulnerabilities in expedition travel and draws attention to biological risks that remain poorly understood. Here are five things to know about the outbreak.
1. The Andes virus is the only known hantavirus capable of spreading between humans.
The main reason the MV Hondius outbreak drew international attention was the specific strain involved: the Andes virus.
Scientists have identified more than 40 hantavirus species worldwide, broadly divided into “Old World” strains found mainly in Europe and Asia, and “New World” strains found in the Americas. Most hantaviruses spread to humans through contact with infected rodents or their urine, saliva and droppings, experts told WIRED. The rodents themselves usually do not become ill.
Old World hantaviruses mainly affect the kidneys and can cause bleeding disorders. New World strains, including the Andes virus found in parts of South America, are associated with Hantavirus Cardiopulmonary Syndrome, a severe illness affecting the lungs and heart. Patients can initially develop fever, fatigue and muscle aches before deteriorating into severe breathing difficulty and cardiovascular collapse.
What makes the Andes virus particularly unusual is that it is the only known hantavirus confirmed to spread between humans through prolonged close contact.
According to the World Health Organization, such transmission usually occurs between intimate partners, household contacts or caregivers caring for symptomatic patients over extended periods. Scientists still do not fully understand why the Andes strain can spread this way while most hantaviruses cannot.
Health authorities have thus far linked eight confirmed or suspected cases to the MV Hondius outbreak, including three deaths. WHO officials said the outbreak has remained limited because the virus doesn't spread easily through casual contact in the way COVID-19 or influenza do. The Andes virus nevertheless carries a high fatality rate. Studies cited by health experts show that some New World hantavirus infections in the Americas can kill up to half of infected patients, making even relatively small outbreaks medically serious.
2. The cruise ship’s confined environment created conditions for prolonged close contact, increasing vulnerability.
One major reason health experts have urged calm despite the alarming deaths is that the Andes virus usually requires prolonged close contact with a symptomatic person for transmission between humans. Experts say the virus doesn't spread easily through brief encounters such as passing someone in public, ordinary conversation or short contact in open spaces.
Researchers are still studying the exact mechanisms involved in human transmission. Some evidence from earlier outbreaks in Argentina suggested droplets or aerosols may have played a role in certain crowded indoor settings. WHO officials nevertheless stressed that transmission appears far less efficient than airborne viruses such as SARS-CoV-2, the virus responsible for COVID-19. Scientists also believe people are most infectious when they are visibly ill, which helps public health authorities identify high-risk contacts more effectively.
The Andes virus also has a relatively long incubation period, estimated at up to six weeks in some cases. That means infected travelers may leave one country and develop symptoms much later somewhere else, complicating international monitoring and contact-tracing efforts.
The MV Hondius created conditions unusually favorable for this type of transmission. The expedition vessel carried fewer than 150 people from more than 20 countries in a confined environment for weeks at sea, The Wall Street Journal reports.
Some passengers shared small multi-person cabins with bunk beds, while daily life involved buffet meals, wildlife excursions, lectures, exercise sessions and long hours spent together indoors during rough South Atlantic weather. Several passengers also interacted closely while comforting those who became ill or grieving family members after the first death on board.
WHO technical lead Anaïs Legand said during a briefing, as reported by MIT Technology Review, that the multinational nature of the outbreak aboard a cruise vessel was something health authorities had not encountered before. Even so, WHO officials and outside experts believe the outbreak is unlikely to trigger widespread community transmission because the virus spreads poorly compared with highly contagious respiratory pathogens.
3. The initial response underestimated the seriousness of the outbreak.
One of the most contentious aspects of the outbreak has been the gap between the first on board death and the eventual implementation of strict containment measures. After a passenger died on April 11, passengers were informed by the ship’s captain that there was no evidence of a contagious threat on board, according to the WSJ. In a video later circulated online, the captain told guests, “We’re not infectious; the ship is safe.” At that stage, Oceanwide Expeditions said, the cause of death remained unknown and medical reviews had treated the case as isolated.
Passengers, therefore, continued much of their daily routine on board. Travelers attended buffet meals, lectures, exercise sessions and wildlife excursions together, while some shared small multi-person cabins for days at sea. Several passengers later reported that, based on available information, they believed the situation was under control.
The situation became more serious during the second leg of the voyage after passengers had already disembarked at places including Tristan da Cunha and St. Helena. A second critically ill passenger was evacuated from the ship on April 27. At that point, the cruise line activated the highest level of its emergency response plan, introducing isolation measures, hygiene protocols and medical monitoring. By then, multiple passengers had fallen ill, and several required urgent medical evacuation.
Passenger and Turkish YouTuber Ruhi Çenet later said he wished the situation had been treated more seriously earlier in the voyage, according to the WSJ. He recalled seeing the wife of the first passenger who died struggling to stand while traveling through Johannesburg after leaving the ship.
Health authorities later identified confirmed cases as the Andes strain of hantavirus.
4. Investigators believe the virus was brought on board before the voyage began.
One of the most important findings from the investigation so far is that the outbreak likely did not begin on the ship itself. According to statements from the WHO and reports from Argentina’s health ministry, the couple linked to the earliest known infections had traveled through Argentina, Chile and Uruguay on a birdwatching trip before boarding the MV Hondius in Ushuaia, MIT Technology Review reported.
WHO officials said the first infected passenger probably contracted the Andes virus during that earlier journey through regions where rodents known to carry the virus are prevalent.
The WHO is now working with Argentine authorities to retrace the couple’s movements before they boarded the ship. Argentina’s health ministry said rodents in Ushuaia would also be trapped and tested for the Andes strain as investigators attempt to identify the likely source of exposure.
That early exposure became especially dangerous because the Andes virus has a long incubation period. The MV Hondius itself then created the kind of prolonged close contact that health officials later said was necessary for human-to-human transmission.
The exposure chain widened further once the ship reached inhabited islands. At Tristan da Cunha, one of the world’s most remote inhabited territories, passengers disembarked for tours and social visits, according to the WSJ. Travelers drank beer with island residents at the Albatross Pub. A passenger and two crew members from the vessel also gave a presentation to local schoolchildren. And local officials boarded the ship for a photo opportunity with the captain. Six new passengers also joined the vessel there before it departed again.
The next major stop was St. Helena, where 29 passengers disembarked on April 24, including the wife of the first passenger who died on board. Some passengers stayed in hotels on the island before continuing onward travel through Johannesburg and other international transit routes. Çenet, the YouTuber from Turkey, was quoted as saying that he saw the dead passenger’s wife struggling to stand upright at Johannesburg airport before she later died there.
By then, the outbreak had already moved beyond the ship itself. Another passenger who disembarked at St. Helena later tested positive in Zurich, Switzerland, according to MIT Technology Review. WHO officials later said they were receiving reports of suspected cases connected to passengers who had already traveled onward internationally. Health authorities in several countries, including the United States, Britain and Switzerland, began tracing contacts connected to the voyage.
What may have begun as a single rodent exposure during a birdwatching trip in South America had by then expanded into a public health investigation stretching across cruise passengers, remote island communities, hotels, airports and multiple national health systems.
5. There is no vaccine or specific cure for the Andes virus.
There is no vaccine or antiviral treatment for the Andes virus. Doctors can only provide supportive medical care while trying to keep patients alive long enough for their bodies to fight the infection.
The virus can become deadly because of the way it attacks the lungs and cardiovascular system. Patients often begin with symptoms resembling ordinary flu, including fever, fatigue, muscle aches and dizziness. In severe cases, however, the condition can rapidly deteriorate into breathing difficulty, pneumonia and cardiovascular collapse.
Scott Weaver, a hantavirus researcher at the University of Texas Medical Branch, told WIRED that the blood vessels begin leaking fluid into the lungs, making breathing progressively more difficult even with medical intervention.
The WHO says early intensive care is critical for survival. Treatment mainly involves monitoring breathing, managing fluid levels carefully and providing oxygen support or intensive respiratory care when necessary.
Tedros Adhanom Ghebreyesus, the WHO director general, said health authorities believed the outbreak would remain limited if containment measures were implemented.
The outbreak has renewed concerns about global preparedness for infectious disease emergencies. All full-time employees in the U.S. Centers for Disease Control and Prevention’s Vessel Sanitation Program had reportedly been laid off last year, MIT Technology Review noted. Public health experts fear such reductions could weaken preparedness for future outbreaks involving international cruise passengers.
WHO officials said no new symptomatic cases had been identified on board, which they described as an encouraging sign despite the virus’s long incubation period.
This article was originally seen on The Christian Post.
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