Two studies detail how the hantavirus outbreak spread on board the Hondius and link its genetic lineage to Patagonia

Hantaviruses are transmitted via aerosols originating from rodent excretions or secretions; these viruses are geographically linked to their hosts. The articles suggest that, contrary to other assumptions, the genome of the Andes virus is similar to that of the cases that emerged on the cruise ship, suggesting that there has been the international spread of a virus that was already known to be capable of human-to-human transmission under certain conditions. However, other hypotheses regarding the infection are also put forward, such as the existence of mixed viral populations or more than one zoonotic infection.

Another important point is the overlap in the incubation period for hantavirus pulmonary syndrome, which can last up to six weeks. This raises the possibility of an infection prior to boarding or some other form of exposure during the early stages of the voyage, which does not rule out the presence of rodents or other as yet unknown reservoirs on board the ship. This gives rise to two likely scenarios: one is that a zoonotic infection was transmitted to humans before or during the early stages of the voyage, and that subsequent transmission then occurred from person to person.

Be that as it may, we need scientific information that will enable us to make further progress by conducting epidemiological surveillance of the geographical areas where rodents are present, broadening our focus to include other, as yet unknown, hosts, carrying out sero-epidemiological studies of human populations to assess geographical distribution, and sequencing the complete viral genome.

[He has reviewed the article: ‘Hantavirus pulmonary syndrome outbreak linked to cruise ship travel in April–May 2026’].

This is an important study on the Andes virus outbreak aboard the Hondius cruise ship. It analyses the results of a rapid, coordinated multinational investigation, which utilised classical epidemiology (‘field-based’ epidemiology) and genomic analysis. The authors acknowledge several limitations: no sample is available from the index case (case 1); three cases were not sequenced; uncertainties remain regarding some exposures prior to embarkation (the mention of the van in which cases 1 and 2 travelled through Chile and Argentina prior to embarkation is particularly interesting); and it cannot be proven beyond doubt that there was a single initial zoonotic event.

Their main conclusions confirm the basic epidemiology of the Andes virus and the evidence of person-to-person transmission via close and prolonged contact, in this instance in an exceptional setting (an international cruise ship), as well as previous knowledge regarding the lineages of the Andes virus, which essentially rule out the emergence on the cruise ship of a virus that is more transmissible or better adapted to humans.

In summary, it serves as a reminder of how an infectious disease – in this case, a relatively rare zoonosis – can lead to a limited outbreak that became an international incident due to a combination of global mobility, confined spaces and delays in diagnosis. It is a good example of the value of collaboration in investigating outbreaks and highlights the great importance of the ‘One Health’ concept: human, animal and environmental health are closely interlinked.

The two studies published in Science on hantavirus employ a methodology appropriate to their objectives and feature a surprising (sic) number of authors (more than 30 in both cases). The findings confirm what we already knew about the epidemiology of hantavirus and reinforce the appropriateness of standard intervention measures for this specific type of outbreak.