Dengue Fever: Viral Strains in Warm Countries, and How It Shifts

An estimated 2.5 million people live in countries and areas where dengue fever can be transmitted, and 22,000 die from it annually, mainly children, according to the World Health Organization. Researchers at the University of Texas Medical Branch at Galveston; Duke-NUS Graduate Medical School; University of California, Berkeley; and University of Texas School of Public Health, Houston recently published a paper in the journal Science, detailing the ways that dengue develops to increase its ability to cause outbreaks as it travels to new places and revisits old ones--and why some strains of the virus are better suited to cause a widespread outbreak, according to this release.

First, the scientists examined the clades: the common ancestor and all the descendants of that ancestor of dengue virus-2, which is the strain that circulated in Puerto Rico in 1994 when a harsh epidemic broke out. They looked at the differences between the strain seen from 1986 to 1995--and a more potent strain that was first isolated in 1994, according to the release.

An interaction existed, they found, between the newcomer virus' RNA and proteins within the host that allows the virus to bypass the host's immune response. It was at that point easier for the virus to invade, according to the release.

"Firstly, our findings show that not all dengue viruses have the same ability to cause epidemics," said Professor Eng Eong Ooi, who is Deputy Director the Emerging Infectious Diseases (EID) Program at Duke-NUS, in a release. "Secondly, they imply that identifying the molecular signatures that allow the viruses to spread more efficiently could help focus public health resources on more important strains of viruses."