Changing climate may influence risks from deadly rodent-borne diseases

Changes in rainfall can trigger increases in rodent populations and subsequent spikes in infection, new research has found, revealing how a changing climate could have consequences for human health.

The research, led by the Natural History Museum, London, and University of Oxford with collaborators at University College London and other institutions, developed a modelling framework using almost 30 years of data collected by the University of Antwerp on the Natal multimammate mouse (Mastomys natalensis), a widespread African rodent and the main host of Lassa virus.

When tested against more than 6,000 recorded Lassa fever cases in Nigeria, the model accurately predicted the seasonal timing of outbreaks, suggesting it could help scientists identify periods of heightened disease risk.

Lassa fever is a rodent borne zoonotic disease endemic to West Africa. Humans can become infected through contact with infected rodents or food and household items contaminated by their urine or faeces. Severe cases can be fatal. Understanding the environmental conditions affecting these animals is therefore important for identifying when the risk of disease spillover may be greatest.

Using more than 20,000 rodent captures from Tanzania alongside climate and pathogen exposure data, the researchers found that rainfall was a key driver of rodent populations, with wetter conditions likely increasing food availability and stimulating breeding.

Dr Gregory Milne, postdoctoral researcher at the Natural History Museum, who co-led the study said: “The planetary emergency is changing the conditions in which people, wildlife and pathogens interact. To understand what that means for human health, we need to understand the ecological processes connecting environmental change to disease.

“Our research shows how changes in rainfall can drive rodent population booms and influence infection, helping explain why disease risk varies over time. When we applied the model to Nigeria, the timing of peaks in infected rodents closely matched the seasonal timing of human Lassa fever outbreaks.

“Understanding how environmental change affects wildlife populations is essential for anticipating future zoonotic disease risks, and could help scientists and public health authorities identify periods of heightened risk.”

Prof Kate Jones, Director of the UCL People and Nature Lab said: “This shows the value of putting ecology at the centre of zoonotic disease research. Climate alone cannot predict the size of an outbreak, but understanding the ecological processes connecting environmental conditions, wildlife populations and pathogens could help identify periods when the risk of spillover is higher.”

The researchers also found that the virus could persist in rodent populations by passing from mothers to their offspring. Their model estimated that almost 80% of infected pregnancies resulted in this form of transmission, helping the virus survive between breeding seasons.

The impact of rainfall was particularly clear during the 2015–2016 El Niño event, when unusually heavy rainfall in East Africa coincided with a predicted rise in young rodents followed by an increase in infected animals.

The researchers then tested whether their model, built using data from Tanzania where Lassa fever is absent but the multimammate mouse present, could help explain outbreaks in West Africa. Using climate data from five Nigerian states, they compared its predictions with more than 6,000 confirmed Lassa fever cases recorded by the Nigerian Centre for Disease Control and Prevention between 2018 and 2025.

Peaks in infected young rodents tended to occur around a month before peaks in human cases. In 83% of comparisons, the predicted peak in infected rodents and observed peak in human cases were within 28 days of each other.

The model could often predict the timing of outbreaks, but not their size, which is likely to depend on other factors including human behaviour, contact with rodents and disease surveillance.

Climate change is part of a wider planetary emergency in which natural systems are under increasing pressure from biodiversity loss, habitat destruction and other human driven environmental changes. Understanding how species respond to these pressures, and what this means for people, is an increasingly important area of research.

The study forms part of the Museum's and UCL’s wider research into how environmental change affects biodiversity, and how these changes can influence risks to human health.

The new framework goes beyond identifying correlations between climate and human disease outbreaks by examining the ecological processes connecting them. Future climate projections could therefore be used to investigate how environmental conditions may alter wildlife populations, pathogen transmission and zoonotic risk.

The approach could also be applied beyond Lassa fever. Rodents host more zoonotic pathogens than any other group of mammals and respond rapidly to environmental change. Similar models could investigate other climate sensitive host pathogen systems, particularly where human disease data are scarce.

As the planet changes, establishing how climate affects animal populations and pathogen transmission could help scientists anticipate and prepare for future changes in zoonotic disease risk.

The study, ‘Climate-driven host ecology as a framework for zoonotic disease risk: Understanding transferability across arenavirus systems’, is published in Proceedings of the National Academy of Sciences.

ENDS

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About The University of Antwerp

The University of Antwerp is a research university where pioneering, innovative research is conducted at an international level. Research and education are closely linked. Educational innovation is a constant focus, and special care is also taken to welcome and guide each of the 25,000 students spread across our nine faculties. The University of Antwerp is not an island: we build bridges to secondary education, to industry and, by extension, to society as a whole. With over 7,000 members of staff, the University of Antwerp is one of the most important employers in Antwerp, Flanders’ largest city.