For decades, hantavirus was treated as a problem in localised areas. It was rare, and remained a hidden threat in rural corners of the world.
Not anymore, though.
As the world warms in intensity, ecological disruptions are changing what we know about diseases.
An analysis published in Nature Climate Change in August 2022 noted this worrying trend. It found that 218 of 375 infectious diseases affecting humans have at some point been exacerbated by climatic hazards.
Climatic hazard pathways, which result in the aggravation of specific pathogenic diseases. (Nature Climate Change)
Hantavirus is no exception, and neither is its connection with climate change.
According to a review published in the Clinical Microbiology and Infection journal in 2009, it is “reasonable to assume that climate change might influence hantaviruses through impact on reservoir host populations”.
Mice and rats are the primary carriers of hantavirus, shedding the pathogen through their urine, faeces, and saliva. Human infection typically occurs through inhalation of contaminated dust. While many types of hantaviruses exist, only the Andes virus is known to spread from one human to another. The Andes virus is endemic in South America, and is the virus that spread on MV Hondius, killing three people and infecting 11 more so far.
The Pan American Health Organization, in an update published December 19, 2025, noted that South American countries Bolivia and Paraguay reported significant increases in cases of hantavirus pulmonary syndrome (HPS), as compared to historical averages. Argentina continues to be the country with the highest number of reported hantavirus cases in the region.
Deaths and fatality rate due to hantavirus pulmonary syndrome reported in South America, between 2021 and 2025. (Source: Data provided by respective countries to PAHO)
What determines how many rodents exist in a given area, and where they live, is largely a function of the environment.
CLIMATE CHANGE AFFECTS RODENT POPULATIONS?
Changes to the precipitation cycle is among the biggest drivers of changes to rodent populations. This occurs in two ways: in cases of excess moisture due to unusually heavy rainfall, vegetation growth booms. This increases food availability for rodents, driving population. Heavy rainfall and floods can also inundate rodents’ natural habitat, forcing them out, towards human settlements.
In cases where precipitation is below normal, rodents are also driven out in search of food and water, mostly towards human settlements.
Intense and erratic hydrometeorological events are associated with global warming. The atmosphere can hold about 7% more moisture per 1°C of warming. As temperatures rise, the atmosphere’s capacity to hold moisture increases, leading to random, heavy bouts of precipitation. Heat too can delay or reduce precipitation in some areas, bringing in a phenomenon that experts call “weather whiplash”.
Rodents also seek warmer temperatures: breeding cycles begin as the weather gets warmer. Winters were once believed to cull rodent populations naturally, as many of them do not survive the cold and the snow.
“Rodent populations are already expanding into regions considered to present a low risk of hantavirus, in particular, at higher elevations and in temperate regions,” Dr Rajeev Chowdry, Director of Internal Medicine at Yatharth Super Speciality Hospital, Faridabad, said. “If these trends continue for the next ten to twenty years, further expansion of rodent habitat would create considerably larger zones of exposure,” he added.
In a study published in npj Viruses journal on April 15, researchers led by Dr Pranav Kulkarni, veterinary epidemiology researcher at the University of California, Davis, predicted a substantial increase in the risk of arenaviruses for human populations in the next 20 years, in both endemic and non-endemic regions of the world.
Arenaviruses and hantaviruses are not the same, but both are carried by rodents, and the effects on host populations of one can predict changes in the host populations of the other family as well.
“The distribution of rodent species from South America (Venezuela, Argentina, and Bolivia) that we modelled was found to be sensitive to seasonal shifts in temperature, annual minimum-maximum range of temperature, and disruptions in rainfall in key months (wettest month and warmest months of the year),” Dr Kulkarni said.
The researcher also added that at least for arenaviruses, they expect a more diffused spread over a wide geographical range that has previously not witnessed these disease outbreaks. “This is a very worrying prediction in terms of public health and strain on resources,” he said.
LAND USE CHANGE
Land use change alters how frequently rodents and humans interact. Clearing forest lands for agriculture to account for growing food demands pushes humans deeper into ecosystems that were previously undisturbed. This interaction is where the risk of zoonotic spillover is highest.
2 Indian crew aboard ship with deadly hantavirus outbreak, their status unknown
Even occupational and recreational activities in rural areas increase the risk of such interactions. Patient zero for the outbreak that started on MV Hondius was Leo Schilperoord, a Dutch ornithologist who is believed to have picked up the disease while looking for rare birds in a landfill on the outskirts of Argentina’s Ushuaia city, a known hotspot for the Andes virus strain.
WHAT NEXT?
There is no one factor that can explain the changing epidemiology of hantavirus, but we need reliable climate model predictions and monitoring to catch possible outbreaks. “We must also consider the fact, that for reliable forecasts at scale, the models require good quality and granular data for validation that is currently not available either for new world arenaviruses or hantaviruses,” Dr Kulkarni said.
It is also important to note that rodent ecology differs by region and species, making forecast difficult and complex, Dr Chowdry said.
Dr Kulkarni also added that the spillover risk of deadly haemorrhagic fevers can affect millions of people if realised through outbreaks, which can be prevented through climate-adaptive public health planning and transboundary collaboration and sharing of information. “Only through that will we be able to contain and maybe even prevent emergence in new areas. But this discussion needs to happen now.”
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