Endemic for decades in certain regions of Argentina, hantavirus, including the human-to-human transmissible "Andes" strain that spread on board the MV Hondius cruise ship, has given local scientists some expertise in the disease, without removing all the unknowns.
Argentina has recorded 102 cases of hantavirus for the current epidemiological campaign (June to June), after 57 cases in 2024-2025, 75 in 2023-2024, 65 in 2022-2023 and a peak of 126 in 2018-2019.
The rodent and the environment
The vector of the Andes strain is the " raccoon colilargo" , long-tailed pygmy rice paddy rat (Oligoryzomys longicaudatus) by which contagion can occur through contact with excrement, urine or saliva, generally in an enclosed environment. The animal lives in wooded areas where it feeds mainly on seeds, plants and fruits, and is sensitive to variations in the environment.
According to biologist Raul Gonzalez Ittig, professor of population genetics at the University of Córdoba, an increase in cases in Argentina may be linked to a climatic sequence: after two dry years, intense rains associated with the El Niño phenomenon have favored a accumulated vegetation growth and greater food availability for rodents“. More rodents means " a higher probability that a rural worker will be infected", the specialist told AFP.
Contact is made more likely because " Humans have begun to occupy more environments where rodents can reach.“, estimates epidemiologist Rodrigo Bustamante, from Bariloche hospital. And just one rat is enough. to begin the story "triggering a possible mechanism of human-to-human transmission," notes infectious disease specialist María Ester Lázaro, author of a thesis on the Andes strain, recalling documented cases of deadly outbreaks in 1996 and 2018.
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No mutation
However, human-to-human transmission This is not the rule, but an exceptional event that requires close contact, less than one meter for 30 minutes.", emphasizes Dr. Bustamante. Argentine scientists, like their counterparts abroad, dismiss the idea of a mutation that facilitated human-to-human transmission.
“ I think the virus has always had this property", says Dr. Bustamante, according to whom There was no one-off change.“. “ It is a very stable virus, unlike Covid-19 or the flu.“,” Ms. Lazaro emphasizes. “The various hantaviruses have accompanied…” since ancient times with their host rat, without changing“.
Difficult to study
One of the challenges facing Argentinian scientists with the hantavirus It's because there are so few cases" explains Ms. Lazaro. It takes a lot of time to get even a barely adequate number that allows us to draw conclusions. » Mr. Bustamante also judges " It is very difficult to draw representative conclusions.“.
Another difficulty lies in the clinical evolution, with initially benign symptoms that can deteriorate extremely abruptly. “ Within a few hours, the patient can go from a flu-like condition to requiring respiratory support." explains Ms. Lazaro. Like a tsunami. » Hence the difficulties to conduct interviews about patients' journeys, the places they have been, and for clinical testing“.
The case of Tierra del Fuego
In Tierra del Fuego, from where the MV Hondius set sail, there is a debate about whether a local rodent, the Patagonian colilargo (Oligoryzomys magellanicus) is the same or a subspecies of Oligoryzomys longicaudatus, allegedly absent from the province.
According to Juan Petrina, provincial director of epidemiology services, he exhibits morphological and dietary differences“. For Guillermo DeFerrari, a biologist at the Southern Center for Scientific Investigations in Ushuaia, the challenge is to determine whether this local rodent is, or is not, a possible vector of the disease.
Tests to date on rodents in Tierra del Fuego have come back negative for hantavirus. However, an upcoming mission to Ushuaia by scientists from the Malbran Institute in Buenos Aires, a national reference center, will aim to update this finding. Due to the long incubation period, however, infection could have occurred elsewhere than in this territory in southern Argentina.
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