Dr. Anne Schuchat, a deputy director of the Centers for Disease Control and Prevention, told reporters the type of mosquito in which the virus is carried is present in more US states than initially thought.

She cited what authorities are learning about the virus is "scarier than we initially thought." Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, said at a White House briefing the first Zika vaccine candidate should be available in September.

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