Officials say they are making progress in fighting the Zika virus in a small area of South Florida.
On Thursday, we heard from the head of the CDC himself.
Dr. Tom Frieden says there are no new cases in the target area in the Wynwood section of Miami.
And the results indicate the first round of aerial spraying has killed a large portion of the total mosquito population.
Dr. Frieden says they believe the aerial spraying can reach the bugs in places truck or hand spraying can't.
And he says that's what's needed in the dense neighborhood where Zika has invaded.
"You have residential as well as business, industrial, construction and other locations there so that makes it a challenging area," said Dr. Frieden.
The spraying Thursday morning spread pesticides not just over the area where cases of locally-transmitted Zika have been reported, but also across a buffer zone.
The CDC says there is no evidence of the virus anywhere else in Miami, so the rest of the city and South Florida are considered safe.
Miami's mayor wants the spraying to be repeated once a week for a month.
Zika in Florida: CDC says spraying cut mosquito population
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