Hantavirus Outbreak on Cruise Ship Kills Three, Sickens Seven as WHO Investigates Transmission

An outbreak of hantavirus has struck the MV Hondius cruise ship, killing three passengers and sickening seven others during its voyage from Argentina across the Atlantic. The World Health Organization reported two laboratory-confirmed cases and five suspected ones, with investigations ongoing into the source of infection.

The vessel, operated by Oceanwide Expeditions, remains moored off the coast of Cape Verde as health officials assess the situation. The first illnesses emerged after the ship left Argentina on April 1, with the initial death occurring on April 11. Another confirmed case involved a British citizen evacuated to South Africa for treatment.

Experts suggest the virus likely originated from rodents, as hantaviruses are typically transmitted through aerosolized particles from infected animals' urine, feces, or saliva. Kartik Chandran, a virologist at Albert Einstein College of Medicine, explained that people contract the virus by breathing in these particles, often stirred up during cleaning activities.

Sabra Klein, a viral immunologist at Johns Hopkins Bloomberg School of Public Health, noted that infected rats could have boarded the ship, where vacuuming might have released the virus into the air. Alternatively, some passengers may have been exposed before boarding.

Michelle Haby, an epidemiologist at the University of Sonora, pointed out that symptoms can appear one to eight weeks after exposure, aligning with the ship's departure from Argentina, where the Andes strain of hantavirus is endemic. WHO's Maria Van Kerkhove stated that the organization is working under the assumption that the deceased Dutch couple contracted the virus during a wildlife excursion in Argentina prior to embarkation.

“Our assumption is that has happened. Haby's review of cases in Chile and Argentina found strong evidence of such spread in only a few instances, emphasizing that it requires very intimate contact. On the ship, WHO is investigating whether this occurred among close contacts, though Van Kerkhove noted that if it were highly infectious, far more cases would be expected. To contain the outbreak, passengers are isolating in cabins, wearing masks, and practicing social distancing. Jake Rosmarin, a passenger aboard the ship, described measures including meal deliveries to cabins and restricted access to indoor common areas, while outer decks remain open for fresh air. He praised the crew's efforts to maintain safety and cleanliness, countering suggestions that the vessel is unclean. The ship reached Saint Helena on April 22 with the first victim on board. Two crew members are currently ill, and one passenger was evacuated to intensive care in South Africa. Medical teams in protective gear have boarded to test and treat those showing symptoms, which include fever, chills, headache, nausea, and in severe cases, respiratory failure.”

Hantavirus can cause severe illnesses, with New World strains like Andes leading to hantavirus pulmonary syndrome, which has a fatality rate of up to 35 percent. Old World strains may cause hemorrhagic fever with renal syndrome, with fatality rates ranging from less than 1 percent to 12 percent.

Not all exposed individuals develop symptoms, and many recover with supportive treatment, though older people with comorbidities face higher risks. WHO is collaborating with multiple countries for contact tracing, laboratory testing, and evacuations.

The organization assesses the risk to the general public as low. Van Kerkhove emphasized priorities of keeping passengers and crew safe while limiting spread. The MV Hondius, an expedition vessel rather than a traditional cruise ship, operates with strict biosecurity protocols due to its visits to remote areas.

Rosmarin highlighted its high maintenance standards, especially in environmentally sensitive regions. Authorities in Cape Verde have not permitted docking as a precaution to protect public health. The ship is scheduled to continue to Spain's Canary Islands, where health officials will conduct a thorough investigation and disinfect the vessel.

Prof Jonathan Ball from Liverpool School of Tropical Medicine discussed the virus's origins in a podcast, noting its transmission from rodents to humans and efforts by health agencies to contain it. While most hantavirus infections are zoonotic and accidental, this outbreak has drawn attention due to its rarity at sea and the absence of vaccines or cures.

Questions remain about whether rodents are present on the ship, as no such findings were reported, or if all exposures occurred on land. Ongoing detective work aims to clarify the transmission dynamics, with experts like Chandran describing the virus's mechanism of infecting human cells through glycoproteins that facilitate entry after aerosol inhalation.