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January 19, 2016
People infected with dengue virus who don’t exhibit symptoms can transmit the virus to mosquitoes, suggesting that asymptomatic dengue infections contribute to virus transmission more than has been recognized in the past, report an international group of researchers (Duong V et al. Proc Natl Acad Sci U S A. 2015;112:14688-14693).
About 75% of all dengue infections are clinically inapparent and are generally considered “dead-end” hosts for dengue virus (DENV) transmission because viremia levels are not thought to be high enough to infect Aedes aegypti mosquitoes, the primary vectors of DENV. Investigators tested this assumption in a human population at risk of dengue infection in the town of Kampong Cham, Cambodia. The researchers fed laboratory-raised mosquitoes with blood from 181 people who had been in contact with hospitalized patients with dengue symptoms and had detectable plasma levels of dengue virus RNA. Among the participants, 126 were symptomatic when the mosquito feeding took place, 42 developed symptoms after feeding, and 13 were asymptomatic.
The investigators found that despite having lower levels of the virus, asymptomatic and presymptomatic individuals were about 10 and 5 times more likely, respectively, to successfully transmit DENV to mosquitoes through direct feeding relative to symptomatic people. The findings underscore the importance of inapparent human DENV infection and measuring viremia when evaluating the risk of disease transmission.