Climate Change May Spread Arenaviruses and Hantaviruses to New Regions

Shifts in rainfall patterns and warming temperatures may drive deadly rodent-borne arenaviruses into new regions of South America, potentially exposing populations with little prior immunity to severe hemorrhagic diseases.

According to a study published April 15, 2026, in the journal npj Viruses, researchers from the University of California, Davis, found that climate change is likely to expand the habitats of rodents that carry these pathogens. The study indicates that these viruses could move into areas where they have not previously been a threat, increasing the risk of spillover events into human populations.

The research specifically focused on three New World Arenaviruses: the Guanarito virus, the Machupo virus, and the Junin virus. These pathogens are linked to severe hemorrhagic fevers, which can be fatal. Mortality rates for these diseases are reported to range from 5 percent to 30 percent.

Predictive models used by the researchers combined land use patterns, rodent habitat changes, human infection risk, and climate projections to determine how these viruses might spread as the environment changes. The models suggest that rising temperature variability and the expansion of urban and agricultural land within rodent habitats are primary drivers of this increased risk.

The study identifies specific geographic shifts for each virus. The Guanarito virus could potentially extend its reach into northern Brazil and Colombia. The Machupo virus may shift toward the mountain regions of Bolivia, while the Junin virus is projected to move into new areas of Argentina, even as risks decline in other parts of the country.

Pranav Kulkarni, a veterinary epidemiologist at the University of California, Davis’s Weill School of Veterinary Medicine, expressed concern that these emerging threats are not currently being prioritized by health authorities.

Kulkarni stated that that’s the worrying part and noted that these diseases are not on the public health officials’ radar.

The risk is particularly high for farmworkers who operate in areas inhabited by infected rodents. However, as climate change pushes these animals into new territories, the risk of infection may extend to broader communities.

Medical options for treating arenavirus infections remain extremely limited. There are currently no approved treatments for these diseases. While a vaccine for the Junin virus exists and is licensed in Argentina—and may offer some protection against the Machupo virus—most affected populations lack access to preventative measures.

The threat of rodent-borne illness in the region is further highlighted by recent events involving other pathogens. The Andes virus, a type of hantavirus, recently sickened several passengers on a cruise ship that began its voyage in Argentina, resulting in some deaths.

To combat these emerging risks, the researchers utilized AtlasArena, an open-source platform designed to track climate-sensitive zoonotic diseases. The platform is intended to help identify emerging hotspots that require long-term public health planning and cross-border surveillance to prevent outbreaks before they occur.

The findings emphasize the intersection of environmental change and public health, suggesting that the movement of wildlife driven by climate instability can introduce dangerous pathogens to unprepared healthcare systems and vulnerable populations.