Weather forecasters are already warning about an intense El Niño season that’s expected to alter precipitation levels and temperatures worldwide. El Niño seasons, characterized by warmer Pacific Ocean water along the equator, may impact the spread of some infectious diseases transmitted by mosquitoes.
In a study published last month in the Proceedings of the National Academy of Sciences, researchers reported a link between intense dengue fever epidemics in Southeast Asia and the high temperatures that a previous El Niño weather event brought to that region.
Dengue fever, a viral infection transmitted by the Aedes mosquito, can cause life-threatening high fever, severe joint pain and bleeding. Infection rates soar every two to five years. Interested in understanding why, an international team of researchers collected and analyzed incidence reports including 3.5 million dengue fever cases across eight Southeast Asian countries spanning an 18-year period. The study is part of Project Tycho, an effort to study disease transmission dynamics by mining historical data and making that data freely available to others.
The data suggest that an increased incidence of dengue fever corresponded to periods of higher temperatures driven by strong El Niño events. As shown in this video featured in an NIH Director’s Blog post about the work, the pattern is most notable in 1997 and 1998, when the last major El Niño event occurred. One possible explanation: The Aedes mosquito reproduces faster and transmits the virus more efficiently at higher temperatures. Additional factors, such as people’s travel patterns and susceptibility to the circulating virus, also likely contributed.
The current El Niño season will offer the researchers an opportunity to further investigate the pattern they observed in Southeast Asia. They plan to update the current dataset and conduct disease forecasting studies. “This is an unprecedented international effort to truly forecast and test predictions based on real-world and real-time data,” says Wilbert van Panhuis of the University of Pittsburgh, who helped lead the study.
Increased temperatures during a strong El Niño season might also impact other vector-borne diseases. The research team is currently investigating chikungunya disease, another fever-causing infection spread by the Aedes mosquito.
The current and ongoing work, says van Panhuis, could bring about “fundamental improvements in the way climate and epidemiological data are used together for disease risk prediction at a regional scale.”