Climate change is pushing rodent species — and the deadly hemorrhagic viruses they carry — into parts of South America that have never encountered them before. A new UC Davis study maps where outbreaks could emerge in the next 20 to 40 years.
Millions of people across South America may soon face exposure to deadly rodent-borne viruses they have never encountered before, according to a new study from the University of California, Davis. As rising temperatures and shifting land use alter where rodents live, the dangerous arenaviruses those animals carry are expected to follow — crossing into regions with little or no immunity to them.
The findings were published April 15 in the journal npj Viruses.
“As climate change accelerates, our study shows how the outbreak risk of dangerous New World arenaviruses could ride on shifting rodent populations to reach millions more people across South America,” lead author Pranav S. Kulkarni, a postdoctoral scholar in the UC Davis Weill School of Veterinary Medicine and its Department of Population Health and Reproduction, said in a news release.
What Are Arenaviruses?
South American New World arenaviruses are a family of pathogens capable of causing severe hemorrhagic fevers — illnesses marked by high hospitalization rates and fatality rates ranging from roughly 5% to 30%. Three of the most significant include the Guanarito virus, found mainly in Venezuela and Colombia; the Machupo virus, circulating in Bolivia and Paraguay; and the Junin virus, which affects parts of Argentina.
Despite causing multiple human outbreaks over the decades, these viruses remain far less studied than their Old World counterparts, such as Lassa fever in Africa. That research gap makes accurate risk forecasting especially challenging — and especially important.
How the Study Was Built
To fill that gap, researchers developed an interactive, open-source modeling platform called AtlasArena, funded by the Wellcome Trust. The platform combines climate projections, habitat suitability data for six rat and mouse species linked to these viruses, human population density, and transmission risk — all fed into machine learning models.
That computational approach allowed the team to detect intricate relationships among climate patterns, land use changes, rodent ecology and human exposure risk that simpler models often miss.
“Our study connects the dots between changing climatic conditions and land use, shifting rodent populations and human infection risk, making it possible to see where the next generation of zoonotic arenaviral outbreaks could emerge,” added senior author Pranav Pandit, an assistant professor of veterinary epidemiology in the UC Davis Weill School of Veterinary Medicine.
Where the Viruses Are Headed
The model’s projections paint a clear picture of geographic expansion. The Guanarito virus, currently concentrated in central Venezuela, is expected to spread into parts of Colombia, border regions of Suriname, and northern Brazil. The Machupo virus is projected to migrate from the lowland plains of Bolivia toward the Andes foothills and mountain zones. The Junin virus in Argentina is forecast to retreat from some grassland areas while advancing into others — shifting rather than simply shrinking its range.
In each scenario, the communities in newly affected zones would be encountering these viruses for the first time. Without prior exposure, those populations may be significantly more vulnerable to infection and severe disease outcomes. The primary drivers behind these shifts are changes in temperature, precipitation, and expanding agricultural or urban development within rodent habitats.
Why It Matters for Public Health
The implications extend well beyond the borders of any single country. Researchers say the findings underscore the need for coordinated, climate-adaptive public health strategies that cross national lines — a significant ask in a region where surveillance resources are often limited.
“The first thing a study like this can inform is where we expect the risk to increase,” Kulkarni added. “Then we can look at why it is happening in more detail, identify ways to reduce the risk, and start planning for the long term and ways to reduce the spread of disease.”
For college students pursuing careers in public health, epidemiology, environmental science or global development, the study illustrates how climate change is not a distant or abstract threat — it actively reshapes the geography of infectious disease in real time. Understanding those dynamics is increasingly essential preparation for health professionals entering the field.
An Open Tool for Ongoing Research
The AtlasArena platform is freely available and designed to evolve. Researchers say its framework can be adapted to study other poorly monitored, climate-sensitive diseases spread by animals — making it a potentially valuable resource for surveillance teams, policymakers and scientists worldwide.
Source: University of California – Davis