UM-Led Team Predicts Dengue Fever Outbreaks in the Tropics

CLIMATE-BASED MODEL, THE FIRST OF ITS KIND, LINKS GLOBAL CLIMATE CHANGE TO LOCAL DISEASE VECTORS

Dengue hemorrhagic fever (DHF), considered the most dangerous vector-borne viral disease in the world, each year puts 2.5 billion people at risk and strikes between 50 and 100 million. It causes rashes, severe headaches and joint pain, high fevers, and in some cases death. But an interdisciplinary research team led by Professor Douglas Fuller, chair of the UM Department of Geography and Regional Studies, may help to alleviate the situation. He and his colleagues, based at UM and the University of Costa Rica, have created the first model using climate variables and vegetation indices to predict potential dengue epidemics in Costa Rica.

According to the researchers, the model can predict dengue fever epidemics with 83-percent accuracy up to 40 weeks in advance, while providing information on the magnitude of subsequent epidemics. The model can be expanded to include the broader region of Latin America and the Caribbean, where incidence and spread of the disease has increased dramatically over the past 25 years.

Up close with Aedes aegypti, a mosquito which transmits Dengue Fever. These mosquitoes breed in stagnant pools close to human dwellings.

“Such a tool will provide sufficient time for public health authorities to mobilize resources to step up vector-control measures, alert at-risk populations to impending conditions, and help health professionals plan for increased case loads,” Fuller said.
The mosquitoes that transmit the disease breed in stagnant pools—in discarded tires, flowerpots, old oil drums, and water- storage containers—close to human dwellings. Unlike the mosquitoes that cause malaria, dengue mosquitoes bite during the day—a trait that allows for greater human exposure.

The UM and Costa Rica team’s research looked closely at climate and vegetation variables—such as seasonal vegetation dynamics that affect evaporation and humidity near the ground—which affect mosquito populations. They also studied sea-surface temperature variations in the Pacific Ocean, otherwise known as El Nino. “Now we see more clearly,” said Fuller, “that global climate oscillations such as El Nino are important drivers of disease” in that they can exacerbate problems such as dengue fever by allowing the vectors to spread to more temperate areas. Thus the model, its methods, and its findings contribute to the rapidly emerging field of study that links climate and infectious disease.

Some of the model’s results were published earlier this year in the Institute of Physics’ journal Environmental Research Letters. Among other findings, the article noted that the model reproduced a major dengue epidemic that affected Costa Rica in 2005. The researchers now plan to test the model with data from Trinidad to Singapore, Fuller said. “All indications show that it will work in these places.”