The Aedes aegypti aegypti subspecies of mosquito, which has become a "domestic" pest worldwide, can acquire and transmit Zika virus more easily than its African forerunner. This finding by Fabien Aubry and colleagues could help explain why the virus hasn't caused large-scale outbreaks yet on the African continent. Zika virus disease is associated with an increased risk of microencephaly and other congenital malformations and neurological diseases such as Guillain-Barré syndrome. The virus is transmitted by Ae. aegypti aegypti, which thrives in intertropical urban environments, laying its eggs in water storage containers and trash and preferentially biting humans. But it's not just this closer proximity to humans that makes the mosquito such a potent vector for Zika, Aubry et al. write. After testing 14 lab mosquito colonies developed from field samples collected in Asia, Africa, and the Americas, the researchers found that the African mosquitoes were less likely to acquire Zika virus in their blood meals, and therefore had lower amounts of the virus to transmit when they fed on mice. Genetic differences located on the mosquito chromosome 2 are likely the cause of the increased susceptibility to Zika virus found in Aedes aegypti aegypti outside of Africa, they concluded.