Dengue epidemic likely to be more severe next year

A major increase in cases of dengue will likely occur throughout Southeast Asian countries early next year, researchers have warned.

This is because the most intense El Nino in nearly two decades is emerging in the Pacific, said the study that found that epidemics of dengue are linked to high temperatures brought by the El Nino weather phenomenon.

"Dengue infects large numbers of people across the tropics each year, but incidence can vary dramatically from year to year in any setting," said senior author of the study Derek Cummings, professor at University of Florida in the US.

"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 noted.

The researchers found that an increase in dengue incidence swept through most countries of Southeast Asia in 1997 and 1998 during a historically intense El Nino weather event.

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. 

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.

The international team involved scientists from 18 institutions around the world, including the ministries of health in each study country.

"Now that the new El Nino has started, these findings will help us prepare for a worst-case scenario, and immediate measures can be taken to counter its effect in the next few months," study co-author lam Sai Kit, professor at the University of Malaya in Malaysia, pointed out. 

The findings appeared in the journal Proceedings of the National Academy of Sciences.