Mysterious Zika infections in Florida
Health officials in Florida are investigating four cases of Zika that do not appear to be related to travel, BBC says.
So far cases outside of Latin America and the Caribbean, where the virus is prevalent, have been spread by travel to that region or sexual transmission.
The four Florida cases have raised the possibility that mosquitoes in the US have begun to carry the virus.
Zika causes only a mild illness in most people but the virus has been linked to severe brain defects in newborns.
Florida officials say they have not drawn any conclusions and are still looking into how the virus was transmitted.