The US Center for Disease Control and Prevention has said there was enough evidence to confirm that the Zika virus could cause unusually small heads and brain damage in infants born to infected mothers.
The conclusion should settle months of debate about the connection between the infection and these birth defects, called microcephaly, as well as other neurological abnormalities, the centre said on Wednesday.
"There is no longer any doubt that Zika causes microcephaly," said Thomas R. Frieden, the Center's director.
He said the conclusion, reached after evaluating "mounting evidence from many studies," signifies "an unprecedented association" in medicine, The New York Times reported.
"Never before in history has there been a situation where a bite from a mosquito can result in a devastating malformation," Frieden said.
He and other agency officials said they hoped that the announcement increased awareness and concern about the potential threat to Americans who travel to affected areas in Latin America and those living in Puerto Rico, American Samoa and Southern states where the virus is expected to arrive later this year.
About 700 people in the United States have been infected with the Zika virus as of last week, including 69 pregnant women, the centre announced on Monday.
About half of the cases are in Puerto Rico, where the virus is circulating locally. Most of the other American cases have occurred in people who travelled to South America.
