The role of weather and environmental conditions in malaria transmission has long been recognized. Rainfall, temperature, and standing water all influence the life cycle of the female Anopheles mosquito, which spreads the malaria parasite Plasmodium falciparum. But what drives the conditions that make malaria outbreaks more or less likely?
A new study published in Communications Medicine found that temperatures in the Atlantic and Indian Oceans influence malaria risk in Malawi by altering the country’s environmental conditions. The researchers identified soil moisture as the key link connecting distant ocean temperature patterns to local malaria transmission.
Their work forms the basis for a potential forecasting tool, a much-needed innovation in a country like Malawi, where malaria remains one of the most prevalent infectious diseases, accounting for 7 million morbidity cases and 36% of outpatient visits in 2025.
Unlike rainfall and temperature, which fluctuate from day to day, sea surface temperatures evolve more slowly, making them potentially useful as malaria early-warning systems.
“In Malawi, there haven’t been a lot of studies on early warning signs for malaria transmission. So this was a first step in that direction.”
“In Malawi, there haven’t been a lot of studies on early warning signs for malaria transmission. So this was a first step in that direction,” said Maxwell Elling, a climate scientist at the University of Colorado Boulder and lead author of the study. “The idea is to incorporate all these factors that have a strong relationship with malaria and build a sort of statistical forecast that can help you, months in advance, to make a prediction of malaria incidence for that period.”
“Climate drivers like moisture and temperature don’t just affect the survival rates and habitats of vectors like mosquitoes but also of the pathogens themselves, including malaria parasites,” said Jessie Abbate, an infectious disease ecologist at the University of Virginia who was not involved in the study.
“These pathogens also have a range in which the weather is favorable for their development,” Abbate said. “So understanding how climate drivers influence changes in the weather and environment is hugely important.”
The team combined 19 years of district-level malaria records from Malawi with satellite and atmospheric datasets tracking sea surface temperatures, rainfall, and soil moisture. They then searched for ocean regions whose temperature fluctuations most strongly coincided with changes in malaria incidence.
“Oceans set off wave-like distributions and pressure that drive global winds,” Elling said. “So we wanted to ascertain how these factors influence weather changes in Malawi.”
Two Oceans, Two Effects
Two regions stood out: the tropical Atlantic Ocean and the central Indian Ocean. The researchers found that the two oceans exerted nearly opposite effects on Malawi’s climate.
When the tropical Atlantic was warmer than average, atmospheric circulation patterns transported warm, moist air into southeastern Africa. Rainfall increased, soils became wetter, and malaria incidence tended to rise.
“By and large, wind from the Atlantic drives the kind of environments that mosquitoes like: It’s warmer, more humid, and the soils are moist,” Elling said.
A warmer Indian Ocean produced a different outcome. Although warmer conditions were associated with some increases in rainfall, the additional heat also increased evaporation, drying out soils and creating conditions that were generally less favorable for mosquito breeding and malaria transmission.
Although previous studies have linked soil moisture to malaria transmission, soil moisture has received far less attention than rainfall and temperature.
“Products have been out there to analyze temperature and precipitation for decades,” Elling said. “But with soil moisture, the apparatus for monitoring, like satellite products, is relatively new.”
In the study, soil moisture emerged as the environmental variable most closely aligned with malaria incidence across Malawi.
“Soil moisture…tells us more about water sitting on the ground, which is an essential influence on the development of mosquitoes and their ability to transmit malaria.”
Unlike rainfall alone, soil moisture reflects the combined effects of precipitation, evaporation, and other land surface processes, making it a more direct measure of mosquito breeding conditions.
“Two main climate and environmental factors that these mosquitoes care about are temperature and standing water,” Elling said. “Soil moisture accounts for standing water better than just precipitation. It tells us more about water sitting on the ground, which is an essential influence on the development of mosquitoes and their ability to transmit malaria.”
Abbate agreed, arguing that as long as a link between soil moisture and infectious disease has been established, as in this study, “soil moisture is a much stronger predictor than precipitation. Because after precipitation events, it is the humidity of the soil that determines how much of that water sits in the ground and affects the development of the mosquitoes.”
A Drier Future but Not Necessarily Less Malaria
The researchers also examined what future climate change could mean for Malawi, a country that has already been described as “on the frontline of the climate crisis.” Using projections from nine global climate models, they found a consistent drying trend across the country by the end of the century. Average soil moisture declined by about 6% under a moderate-emissions scenario and roughly 11% under a high-emissions scenario, though the models disagreed on the magnitude of the change.
However, they cautioned that a drier future would not necessarily mean less malaria. Instead, transmission could shift geographically, becoming less likely in some regions while increasing in others.
Abbate also noted that the practical applicability of these long-term predictions depends on a range of factors, in part because pathogens and vectors can evolve over the course of 10 to 20 years.
“So regardless of how much mapping we do, it may not be what the future actually is,” she said. “A more practical approach would be to keep watching where the risk is increasing per time and shifting resources to those regions.”
More broadly, the researchers emphasized that climate is only one factor shaping malaria risk. Housing quality, health care access, socioeconomic conditions, and public health interventions also influence transmission and would need to be considered in any forecasting system.
Still, by showing that soil moisture connects large-scale climate variability to local transmission conditions, the work suggests that malaria outbreaks may be predictable months before they occur.
—Toluwalogo Niji-Olawepo (@Toluwalogo_), Science Writer