(CNN)Zika was worrying local health officials long before Florida announced the nation's first local transmission from an infected mosquito in late July.
Previously, the virus had already hit US territories, Puerto Rico in particular, and there were almost 1,700 cases in the US, most of them stemming from travelers who had visited a Caribbean or South American country.
But the news out of Florida ramped up concerns. It meant the mosquitoes infected with the virus had arrived in the US, and mosquitoes being far harder to corral and track than humans, concerns about Zika's spread shot to the forefront of many local health departments' agendas.
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