The World Health Organization (WHO) has confirmed that the hantavirus outbreak detected on the MV Hondius cruise ship corresponds to the Andes virus, one of the most dangerous variants of this viral family and the only one with demonstrated capacity for human-to-human transmission.
The outbreak has already caused eight confirmed cases, with three deaths and one person in critical condition admitted to intensive care in Johannesburg. The confirmation has heightened international concern due to the high lethality associated with this strain and its unusual epidemiological behavior within the hantavirus group.
A rare virus with exceptional behavior
Hantavirus is not a single agent, but a broad family of viruses with dozens of identified variants, several of which can infect humans. However, the Andes virus stands out within this group for two particularly relevant characteristics: its high mortality rate, which can be around 30–40% in the most severe cases, and its unique ability to transmit from person to person.
The usual transmission of hantaviruses occurs through the inhalation of aerosols generated by infected rodents, that is, suspended particles from the urine, feces, or saliva of these animals. In the specific case of the Andes virus, another route is added to this one, much less frequent in the rest of the family: transmission between humans through close and prolonged contact, especially in situations where there is exposure to bodily fluids.
From rodents to human contagion
The natural reservoir of this virus is not humans, but rodents. In the Southern Cone of America, the main carrier of the Andes virus is the long-tailed mouse, a species widely distributed in the region. For years, human contagion was considered an indirect phenomenon, limited to contact with environments contaminated by these animals.
However, this hypothesis changed after several outbreaks in Argentina. In 1996, in El Bolsón, cases were identified without contact with rodents but with close links between those affected, which raised suspicion of interpersonal transmission. Later, in the Chubut (2018–2019) outbreak, this possibility was more clearly confirmed. In that episode, some patients attended large social events during the initial phase of the infection, which facilitated the emergence of transmission chains and led to the identification of possible "super-spreaders".
Subsequent investigations demonstrated that the isolation of cases and their contacts significantly reduced the spread of the virus, which made it possible to contain the outbreak when the reproductive number fell below the epidemic threshold.
Enhanced surveillance amid an outbreak in a closed environment
The current outbreak is especially relevant for having occurred in a closed environment such as a cruise ship, where close coexistence between passengers and crew can favor transmission if cases are not detected and isolated quickly.
In parallel, the epidemiological situation in Argentina, the country of origin of the virus, already showed in 2026 an increase in virus activity, with dozens of confirmed cases and a lethality higher than that observed in previous years. This context has reinforced the attention of international health organizations, which consider this outbreak a critical scenario for evaluating the response capacity to interpersonal transmission of the virus.