Dengue epidemic likely to be more severe next year

According to a new study, epidemics of dengue are linked to high temperatures brought by the El Nino weather phenomenon

A major spike in cases of dengue will occur throughout Southeast Asian countries next year, owing to high temperatures, a new study has claimed.

Epidemics of dengue are linked to high temperatures brought by the El Nino weather phenomenon, researchers said.

The findings are particularly timely as the most intense El Nino in nearly two decades is emerging in the Pacific, raising the concern that a major increase in cases of dengue will occur throughout Southeast Asian countries next year, researchers said.

Researchers said that an increase in dengue incidence swept through eight countries of Southeast Asia in 1997 and 1998 during a historically intense El Nino 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 senior author Derek Cummings, professor at University of Florida, at the time of the study.

"During years of large incidence, the number of people requiring hospitalisation and care can overwhelm health systems," said Cummings, who is now at Johns Hopkins Bloomberg School of Public Health.

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 travelling waves of large epidemics moving to nearby rural areas.

Travelling waves were found to emerge from multiple urban centres across Southeast Asia, researchers said.

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 synchronisation of incidence across such a large area, spanning thousands of kilometres, 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," he said.

The team involved scientists from 18 institutions around the world, including the Ministries of Health in each study country.

"This study will contribute toward a better understanding of the cyclical nature of dengue," said co-author Lam Sai Kit, a professor at the University of Malaya in Malaysia.

"Based on the extensive data analysed and the conclusions reached, it will help to improve early-warning systems for impending large outbreaks in the region," said Sai Kit.

The study was published in the journal PNAS.