"There is no longer any doubt that Zika causes microcephaly," Dr. Thomas R. Frieden, the C.D.C. director, said at a press conference Wednesday. Dr. Frieden added that the link, arrived at after "mounting evidence from many studies," represents "an unprecedented association" in medicine.
"Never before in history has there been a situation where a bite from a mosquito can result in a devastating malformation," he explained.
The news comes as the disease continues to pose a threat to multiple Latin American and Caribbean countries, as well as the southern United States, where it is expected to spread as "mosquito season" arrives. Candice Burns Hoffmann, a press officer with the National Center for Emerging and Zoonotic Infectious Diseases, 'said" southern areas of the U.S. have the highest risk due to weather conditions.
Only about 1 in 5 people infected with the virus experience symptoms, according to the CDC. Symptoms are generally mild, including fever, rash, joint pain and conjunctivitis – and last for about a week. However, the link between Zika infection during pregnancy and microcephaly is cause for concern. The U.S. Centers for Disease Control and Prevention has advised pregnant women to delay travel to these areas because of Zika's link to the rare birth defect.
There are currently no vaccines or treatments for Zika. However, scientists are working on developing both.
Dr. Sonja A. Rasmussen, the CDC's director of public health information, hopes the definitive link will increase awareness of the disease at a crucial time and place more pressure on Congress to allocate the full $1.8 billion in emergency funding requested by President Obama to fight the disease.
As of April 6, there have been no locally-acquired Zika cases in the U.S., though 346 travel-associated cases have been reported.