Zika virus is transmitted to people primarily through the bite of an infected Aedes species mosquito - Aedes aegypti, shown here, and Aedes albopictus. The same mosquitoes spread dengue and chikungunya viruses. Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites. CDC photo by James Gathany