Florida authorities are reporting what is believed to be the first evidence of local Zika transmission in the continental United States, concluding that mosquitoes likely infected four people with the virus that can cause rare but serious birth defects.
Governor Rick Scott said the state believed active transmission of the virus was occurring within an area of the city about the size of a square mile (2.6 square kms).
Testing showed that one woman and three men had been infected, Scott said.
While health officials have yet to identify mosquitoes carrying the virus, the state has ruled out other means of transmission, including travel to another country with a Zika outbreak, and sexual contact.
Zika's greatest risk is infection in pregnant women, as it causes microcephaly in babies, a condition defined by small head size that can lead to developmental problems.
The current outbreak was first detected in Brazil last year and has since spread rapidly through the Americas.
Florida Surgeon General Celeste Philip said that health officials are not advising pregnant women in the transmission area to move.
The local health department is searching for other potential infections, with more than 2300 people tested so far, as well as ramping up mosquito control programs and is distributing Zika protection kits to pregnant women at their doctors' offices, Florida officials said.
US health officials have cautioned for months that the summer mosquito season was likely to bring local outbreaks, with Gulf Coast states such as Florida, Texas and Louisiana, on the frontlines.
Some have said Zika's spread could be more limited than in places like Brazil, given widespread use of screens on windows, air conditioning and mosquito control programs.
The US Centers for Disease Control and Prevention said on Friday that it would not recommend limiting travel to Florida.
Until now, the more than 1600 Zika cases in the United States have stemmed from travel to another country with active transmission, as well as a small number of cases of apparent sexual transmission by a person infected outside of the country.
