Study links dengue fever outbreaks with El Niño

New study can help tropical countries prepare

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El Niño cycles can have public health impacts.

Staff Report

This year’s El Niño could bring a widespread dengue fever outbreak across Southeast Asia, scientists said after tracking a link between the disease and warmer temperatures.

The warning came after a team of international scientists found that an increase in dengue incidence swept through eight countries of Southeast Asia in 1997 and 1998 during a historically intense El Niño weather event.

“Dengue infects large numbers of people across the tropics each year, but incidence can vary dramatically from year to year in any setting,” said University of Florida biology professor Derek Cummings, senior author of the study published in the Proceedings of the National Academy of Sciences.“The synchronization of incidence across such a large area, spanning thousands of kilometers, is really striking,” Cummings said. “It suggests that continued multi-country coordination of surveillance for dengue is critical to understanding patterns in each individual country.”

Cummings worked with researchers from each of the affected countries and colleagues at the University of Pittsburgh to compile 18 years of monthly dengue surveillance reports on a total of 3.5 million reported cases.

“During years of large incidence, the number of people requiring hospitalization and care can overwhelm health systems. If we can understand the factors that contribute to these increases, we can prepare for them and act to mitigate the impact of the disease,” Cummings said.

The dengue virus is transmitted by mosquitoes in the tropics and subtropics. Each year an estimated 390 million infections occur globally. Though there is no specific pharmaceutical treatment, supportive therapy can greatly improve outcomes. A number of vaccine candidates are in development but none are currently licensed.

In addition to the finding that increased temperature results in increased incidence across the region, the study also found that urban areas act as dengue epidemic “pacemakers,” giving rise to traveling waves of large epidemics moving to nearby rural areas. Traveling waves were found to emerge from multiple urban centers across Southeast Asia.

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