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Climate change is likely to drive rodent-borne arenaviruses into parts of South America that have never faced these diseases, putting new communities of people at risk, finds a study from the University of California, Davis. 

For in the journal npj Viruses, scientists incorporated climate projections, shifting rodent populations and the risks of human infection into a model to offer an early risk projection for arenaviruses and other diseases in the next 20 to 40 years.

“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,” said lead author , a postdoctoral scholar in the UC Davis Weill School of Veterinary Medicine and its Department of Population Health and Reproduction. 

South American New World arenaviruses

Arenaviruses can cause severe hemorrhagic fevers with high hospitalization rates and fatality rates ranging from about 5% to 30%. South American New World arenaviruses include Guanarito virus in Venezuela and Colombia, Machupo virus in Bolivia and Paraguay, and Junin virus in Argentina. Despite having caused multiple outbreaks in humans, they are relatively understudied compared to Old World arenaviruses, such as Lassa fever in Africa.

With funding from Wellcome Trust, the researchers built an interactive, open-source platform called , to understand how climate change is reshaping the risk of zoonotic spillover for arenaviruses and other hard-to-track viruses. They integrated climate projections, habitat suitability for six rat and mouse species linked to the viruses, human population density, and transmission risk into machine learning models. This approach allowed the team to identify complex relationships among climate, land use, rodent ecology and human exposure that traditional models may miss.

Where arenaviruses may next emerge

“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,” said senior author , an assistant professor of veterinary epidemiology at the UC Davis Weill School of Veterinary Medicine. 

For example, the models project that:

• Guanarito virus, which is found in central Venezuela, is expected to spread to parts of Colombia, the borders of Suriname and northern parts of Brazil. 
• Machupo virus is expected to move from the plains and flatlands of Bolivia to the Andes foothills and mountain regions. 
• Junin virus is expected to move from the grassland regions to other parts of Argentina, reducing risk in some regions while expanding risk to other areas. 
• In all cases, populations with little or no prior exposure would be encountering these viruses for the first time, potentially increasing their vulnerability to infection and severe disease.

The risk of spillover is primarily driven by changes in temperature, precipitation and land use, such as expanding agricultural and urban areas within rodent reservoir habitats.

Coordinated, transboundary public health needs

The authors say the results underscore an urgent need for coordinated climate-adaptive public health policies and transboundary collaboration among countries at risk. 

“The first thing a study like this can inform is where we expect the risk to increase,” Kulkarni said. “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.”

The authors note their work with the AtlasArena platform is ongoing, freely available, and that its insights can be adapted to study other poorly monitored, climate-sensitive diseases spread by animals. 

The study’s additional co-authors include Nuri Flores-Perez of UC Davis and currently San Diego Zoo, and Andie Jian, Brian Bird, Christine Johnson and Marcela Uhart from the UC Davis Weill School of Veterinary Medicine.