Insect-borne viruses can lose some of their vigour during their time in mosquitoes before transmission to a vertebrate host.

Credit: James Gathany/CDC

Gregory Ebel at Colorado State University in Fort Collins and his colleagues infected four mosquito species (including Aedes aegypti, pictured) with West Nile virus, which jumps back and forth between mosquitoes and birds.

Fourteen days later, they isolated the virus from the insects' saliva and organs and sequenced its RNA. They found that viruses from different mosquito species had acquired different sets of mutations. When they put the virus into avian cells, they found that these mutations made it more difficult for the virus to survive, suggesting that it had adapted to living in the mosquito. The findings may help to understand how insect-borne viruses are spread, the researchers say.

Cell Host Microbe http://doi.org/bdxr (2016)