MCALLEN, TX - APRIL 14: A Centers for Disease Control (CDC), flier hangs taped to a door on April 14, 2016 in McAllen, Texas. Health departments, especially in areas along the Texas-Mexico border, are preparing for the expected arrival of the Zika Virus, carried by the aegypti mosquito, which is endemic to the region. The U.S. Centers for Disease Control (CDC), announced this week that Zika is the definitive cause of birth defects seen in Brazil and other countries affected by the outbreak. (Photo by John Moore/Getty Images)
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