Malaria is one of the world's deadliest infectious diseases. Because it is transmitted by mosquitoes, malaria is extremely sensitive to environmental conditions, like rainfall and temperature, that affect mosquito survival and activity. Understanding the climate patterns that influence these conditions is critical for improving malaria forecasting and supporting prevention efforts.
New CIRES-led research shows that temperatures in the tropical Atlantic and Indian Oceans drive year-to-year changes in malaria cases in Malawi. The work, published in Communications Medicine , suggests that soil moisture is the key link between large-scale climate patterns and local malaria cases. Changes in ocean temperatures can influence atmospheric patterns, altering rainfall, weather, and soil moisture levels in Malawi — and wet, soggy soils are a strong indicator for potential outbreaks.
"In countries like Malawi, where there are millions of malaria cases per year, advanced warning of when and where cases might be higher than normal is incredibly useful," said Max Elling, the lead author of the paper and a PhD student in Atmospheric and Oceanic Sciences at CU Boulder and CIRES. "This work helps support malaria forecasts by showing which climate conditions matter and why they affect disease risk."
Elling and his colleagues, including Associate Professor and CIRES Fellow Kris Karnauskas, analyzed global climate data and 20 years of malaria case data to identify the link between climate and malaria variability in Malawi.
They found that temperatures in two ocean basins have the largest impact on malaria cases in Malawi: the tropical Atlantic Ocean and the Indian Ocean.
A warm tropical Atlantic Ocean drives shifts in atmospheric patterns that bring more rain and warmer temperatures in Malawi. These conditions soak soils, creating environments where malaria-carrying mosquitoes can thrive and breed, typically driving a rise in cases.
In contrast, a warm Indian Ocean brings hotter temperatures and variable rainfall to Malawi. These conditions dry out the soil, reducing habitats favorable for mosquito breeding and typically leading to fewer malaria cases.
The work suggests that soil moisture, rather than precipitation, is the strongest predictor for potential malaria outbreaks in Malawi.
"Many studies focus on temperature and precipitation," Elling said. "But there are other factors like soil type that affect how rainfall becomes standing water that mosquitoes like. Soil moisture integrates many hydrological factors, providing a more complete picture."
Models predict future climate change will reduce soil moisture levels in Malawi by 2100. This change could alter malaria transmission and change how and when the country prepares for outbreaks, according to the researchers.
The team's approach provides a foundation for more reliable early warning systems, and shows how important cross-disciplinary collaboration is for climate health work.
"Climate health is interdisciplinary — there are a lot of people working on this from the health side but less from the climate side," Elling said. "This project brought together scientists from climatology, epidemiology, entomology, and hydrology, resulting in a study that links disease not only to environmental factors, but also the large-scale climate drivers and underlying mechanisms behind them."
