The strain of Zika virus that has been linked to thousands of birth defects in the Americas, has been identified close to the African continent for the first time.
US health officials say that 279 pregnant women have tested positive for the infection, and cases of the virus have now been identified on the island of Cape Verde off Africa's west coast.
Meanwhile, US President Barack Obama has strongly criticised Congress for failing to fully support his request for a $1.9 billion package to fight the virus.
Mr Obama said that if the US does not tackle Zika now it would cause more problems later on.
"This is not something where we can build a wall to prevent. Mosquitoes don't go through customs," Mr Obama told reporters after meeting with top health officials in the Oval Office.
"Congress needs to get me a bill. It needs to get me a bill that has sufficient funds to do the job. They should not be going off on recess before this is done," he said.