The head of the CDC is warning Puerto Rico could be "hit hard" by the Zika virus, with tens of thousands of people infected.
And Dr. Tom Frieden says with 34,000 births on the island every year, there's a good chance of microcephaly - babies with abnormally small heads.
He says 1 of every 4 adults in Puerto Rico was infected with chikungunya the first year it went around. It's carried by the same mosquito as the Zika virus.
He again urged Congress to act quickly on President Obama's request for nearly $2 billion to fight the Zika virus.
CDC: Puerto Rico could be 'hit hard' by Zika virus
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