Dengue can be spread back to mosquitoes

A groundbreaking new study has found that the dengue virus can be spread back to mosquitoes by asymptomatic carriers, who are actually more infectious than those displaying symptoms.

Scientists at the Institut Pasteur in Cambodia, the Institut Pasteur in Paris and the CNRS provided proof that people infected by dengue virus but showing no clinical symptoms can actually infect mosquitoes that bite them.

It appears that these asymptomatic people - who, together with mildly symptomatic patients, represent three-quarters of all dengue infections - could be involved in the transmission chain of the virus. These findings question established theories concerning the epidemiology of dengue.

Dengue virus infects 390 million people worldwide each year through the bite of mosquitoes of the Aedes genus. But estimates suggest that 300 million of these people do not present clinical symptoms that are severe enough to be detected by health care systems. It was previously thought that these asymptomatic or mildly symptomatic infections did not reach a high enough level of viremia (the concentration of the virus in the blood) to infect mosquitoes.

This finding raises the possibility that people with few or no symptoms - in other words the majority of those infected by dengue - may actually be contributing to the spread of the virus without realizing it, explained researcher Louis Lambrechts.

The study is published in the journal PNAS.