Climate Change Is Expanding the Range of Deadly Rodent-Borne Viruses in South America
May 12, 2026
Climate change is reshaping the geography of infectious diseases in South America, with rodent-borne viruses like hantavirus and arenaviruses spreading into new regions where populations have never faced these threats before. New research confirms that shifting weather patterns—including altered rainfall and milder winters—are expanding the habitats of virus-carrying rodents, increasing the risk of spillover events where these pathogens jump from animals to humans.
While countries like Argentina and Chile have long battled hantavirus outbreaks, recent data shows a doubling of cases in the past year, with over 100 infections reported between June 2025 and May 2026. Experts warn that without intensified surveillance and public health preparedness, these diseases could become far more widespread—and deadly.
The Growing Risk of Hantavirus Outbreaks
Hantaviruses are a family of viruses primarily transmitted through contact with the urine, feces, or saliva of infected rodents. In the Americas, these viruses cause hantavirus cardiopulmonary syndrome (HCPS), a severe and often fatal respiratory illness. The Andes virus, responsible for recent clusters including the MV Hondius cruise ship outbreak, is particularly concerning because it is the only hantavirus known to spread between people.
Case fatality rates for HCPS can reach up to 50%, making it one of the most lethal rodent-borne diseases globally. In contrast, hantaviruses in Europe and Asia typically have lower mortality rates.
The Role of Climate Change in Rodent Expansion
Researchers from Argentina’s National Council of Scientific and Technical Research (CONICET) have mapped how climate shifts are altering the range of the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), the primary reservoir for the Andes virus. These rodents typically inhabit humid forests and shrublands in southern Chile and Argentina, but climate models predict their habitat will expand eastward toward Argentina’s Atlantic coast—where the majority of the country’s population lives.
“More intensive surveillance and testing are needed across provinces, because the virus might be reaching new areas without us finding out.”
El Niño-La Niña cycles further complicate the risk. In central and southern Argentina, El Niño years bring increased rainfall, stimulating vegetation growth and providing rodents with abundant food and shelter. This leads to rapid population expansion. Meanwhile, milder winters allow more rodents to survive and reproduce, increasing the likelihood of virus transmission.
Beyond Hantavirus: The Emerging Threat of Arenaviruses
A separate study using machine learning to analyze climate projections and land-use changes found that arenaviruses—another family of rodent-borne viruses—will also expand their range due to climate change. These viruses, which include Junín, Machupo and Guanarito, cause severe hemorrhagic fevers with hospitalization rates as high as 30% and fatality rates ranging from 5% to 30%, depending on the strain and access to healthcare.
Researchers predict that climate-induced shifts in temperature and precipitation, combined with agricultural expansion, will increase spillover risk as these viruses move into new regions. The study, published in a peer-reviewed journal, emphasizes the need for public health officials to prepare for potential outbreaks as extreme weather patterns become more common.
These diseases are high-impact but remain neglected in terms of research and public health funding. Without proactive measures, the risk of large-scale outbreaks will continue to rise.
Prevention and the Critical Role of Surveillance
The most effective way to mitigate these risks is through epidemiological surveillance, public education, and early detection. However, funding cuts to Argentina’s health and science sectors have weakened disease monitoring programs, reducing the capacity to detect and respond to outbreaks quickly.
Experts stress that regional coordination and data sharing are essential to identify emerging hotspots and develop targeted public health responses. Improved infrastructure for surveillance could lead to more accurate predictions and better-informed health policies, particularly in countries most vulnerable to climate-driven disease spread.
“Always the most important thing is prevention—epidemiological surveillance and education of the population.”
Key Takeaways: What You Need to Know
- Climate change is expanding the range of virus-carrying rodents in South America, increasing the risk of hantavirus and arenavirus outbreaks.
- Hantavirus cases have doubled in Argentina in the past year, with over 100 infections reported between June 2025 and May 2026.
- The Andes virus is the only hantavirus known to spread between people, with a case fatality rate of up to 50%.
- El Niño-La Niña cycles and milder winters contribute to rodent population surges, raising transmission risks.
- Arenaviruses, which cause severe hemorrhagic fevers, are also expected to spread due to climate shifts.
- Public health preparedness is critical, but funding cuts have weakened surveillance programs in affected regions.
- Prevention relies on surveillance, education, and regional coordination to detect and respond to outbreaks early.
FAQ: Common Questions About Rodent-Borne Viruses
Q: How are hantaviruses transmitted to humans?
A: Hantaviruses are primarily spread through contact with the urine, feces, or saliva of infected rodents. Inhaling airborne particles from contaminated rodent droppings is the most common route of transmission.
Q: What are the symptoms of hantavirus cardiopulmonary syndrome (HCPS)?
A: Early symptoms include fever, headache, muscle aches, chills, and gastrointestinal issues. As the disease progresses, it can lead to severe respiratory distress, requiring immediate medical attention.
Q: Can hantavirus be treated?
A: There is no specific antiviral treatment for hantavirus infections. Supportive care, including oxygen therapy and mechanical ventilation, is critical for severe cases. Early diagnosis and hospitalization improve survival rates.
Q: Are arenaviruses different from hantaviruses?
A: Yes. While both are rodent-borne, arenaviruses cause hemorrhagic fevers with symptoms like fever, bleeding, and organ failure. Hantaviruses primarily affect the lungs and cardiovascular system.
Q: What can individuals do to protect themselves?
A: Avoiding rodent habitats, sealing homes to prevent rodent entry, and using insect repellent can reduce exposure. Public health campaigns should educate communities on recognizing symptoms and seeking early medical care.
The Path Forward: Preparing for a Changing Disease Landscape
As climate change continues to alter ecosystems, the risk of zoonotic disease spillover will only grow. South America’s experience with hantavirus and arenaviruses serves as a warning: without robust surveillance, funding for research, and public health infrastructure, communities in new regions will remain vulnerable to these deadly pathogens.
The solution lies in proactive measures: investing in disease monitoring, strengthening cross-border collaboration, and educating populations about risk reduction. The time to act is now—before these viruses spread further.