In Malawi, millions of people contract malaria each year. Now, researchers have found a surprising new way to predict when outbreaks might surge: by measuring how soggy the soil is.
Scientists at CIRES, the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, discovered that soil moisture acts as a powerful early warning signal for malaria cases in Malawi—more reliable than simply tracking rainfall or temperature alone. The key drivers, they found, are thousands of miles away in the tropical Atlantic and Indian Oceans.
"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 study's lead author and a Ph.D. student in atmospheric and oceanic sciences. His team analyzed 20 years of malaria case data alongside global climate records to uncover the connection.
The mechanism works like this: when tropical Atlantic Ocean temperatures rise, atmospheric patterns shift in ways that funnel more rain and warmth toward Malawi. The result is wet, waterlogged soils—perfect breeding grounds for the mosquitoes that transmit malaria. Conversely, when the Indian Ocean warms, hotter and more erratic rainfall tends to dry out Malawian soils, reducing the standing water where mosquitoes lay their eggs and typically leading to fewer cases.
"Many studies focus on temperature and precipitation," Elling noted. "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."
This finding challenges conventional approaches to malaria forecasting, which often prioritize rainfall and temperature data. The team's research, published in Communications Medicine, suggests that monitoring soil moisture could give health officials precious extra time to prepare—distributing bed nets, stockpiling medications, or mobilizing spraying campaigns before cases spike.
Looking ahead, the researchers emphasize that this kind of early warning system requires teamwork across disciplines. "Climate health is interdisciplinary," 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."
The work may prove especially timely as climate change reshapes the conditions that govern malaria transmission. Models predict that rising global temperatures will alter soil moisture patterns in Malawi, potentially shifting when and where outbreaks occur—and making accurate forecasting more important than ever.