A deadly hantavirus outbreak aboard an Atlantic cruise ship is raising global alarm after health officials warned that rare human-to-human transmission (HHT) may have occurred, a scenario rarely seen with this type of virus.
The outbreak, linked to the expedition vessel MV Hondius, has resulted in at least three deaths and several additional infections among passengers and crew, according to the World Health Organisation (WHO).
Suspected Human-to-Human Transmission of Andes Virus
While hantaviruses are typically spread through contact with infected rodent urine, droppings, or saliva, investigators now believe this outbreak may involve the Andes virus (ANDV), the only known hantavirus strain capable of spreading between humans.
WHO officials said some transmission aboard the ship may have occurred through close contact between passengers, marking a rare example of human-to-human transmission.
The suspected chain of infection has drawn particular attention to a Dutch couple who boarded the ship after travelling in South America, where the Andes virus is endemic. Both later died after developing severe respiratory symptoms.
Experts say this strain is especially concerning because it can spread during the early stages of illness, when symptoms may resemble mild flu, making detection and containment difficult.
A High-Risk Type of Hantavirus in a Confined Setting
The Andes virus is the leading cause of hantavirus pulmonary syndrome (HPS) in South America and carries a fatality rate of around 40%, according to medical data. The illness typically begins with fever, fatigue, and muscle aches before rapidly progressing to severe respiratory distress, often requiring intensive care.
The Andes virus is carried mainly by the long-tailed pygmy rice rat, a common species in rural Argentina and Chile. Apart from the long-tailed pygmy rice rat, the Andes virus is relatively common in the long-haired grass mouse, commonly found throughout South America, but is highest in Patagonia.
Cruise ships present a particularly dangerous environment for such outbreaks due to close quarters, shared ventilation, and prolonged contact among passengers, factors that may have facilitated transmission in this case.
Notably, investigators reported no evidence of rodents on board, further strengthening the theory that the virus may have spread between people rather than through its usual animal vector.
Global Response and Ongoing Investigation
The ship, carrying roughly 150 people, has been held offshore near Cape Verde as health authorities conduct testing and containment measures.
Medical teams have implemented isolation protocols, while some critically ill patients have been evacuated to hospitals in South Africa.
The WHO emphasised that the overall risk to the general public remains low, but the unusual nature of this outbreak has triggered heightened surveillance and international concern.
Scientists are now working to confirm whether the Andes virus is definitively responsible and to understand how the transmission occurred in a maritime setting.
If confirmed, the incident would mark one of the clearest modern examples of human-to-human spread of hantavirus in a confined environment, raising new questions about outbreak preparedness beyond traditional transmission models.
For now, the cruise ship remains a floating quarantine zone and a blunt reminder of how quickly rare pathogens can escalate under the right conditions.
