FLORIDA -- Governor Rick Scott has declared a health emergency in four counties in Florida due to the Zika virus.
At least nine cases of the mosquito-borne illness have been detected in the state.
Health officials believe all of the cases are from people who contracted the disease while traveling to affected countries.
Infectious disease Dr. Vilma Vega of Community Aids Network said, "It looks like we have at least two reported cases in Hillsborough County.
"We've got another couple of cases in Miami Dade and these are rather close... Tampa is not far away from us."
Scott signed the order Wednesday to cover Miami-Dade, Lee, Hillsborough and Santa Rosa counties.
"We also have gotten notice that there's been one sexually transmitted and the first sexually-transmitted case here in the United States," added Dr. Vega, who explained the infection happened when a person returning to the U.S. from Venezuela had contact with an individual in Texas.
A key question is whether a natural infection with Zika virus will provide a lifelong immunity against reinfection.
The Zika virus is linked to brain deformities in babies and is causing concern among public health officials worldwide. The virus is primarily spread through mosquito bites, but investigators had been exploring the possibility it could be sexually transmitted.
U.S. health officials say a person in Texas became infected with Zika through sex, in the first case of the illness being transmitted within the United States.
The mosquito behind the Zika virus seems to operate like a heat-driven missile of disease. Scientists say the hotter it gets, the better the mosquito that carries Zika virus is at transmitting a variety of dangerous illnesses.
Although it's too early to say for this outbreak, past outbreaks of similar diseases involved more than just biology. In the past, weather has played a key role, as have economics, human travel, air conditioning and mosquito control. Even El Nino sneaks into the game.
Scientists say you can't just blame one thing for an outbreak and caution that it is too early to link this one to climate change or any single weather event.
The hotspots for this Zika outbreak also have been temperature and drought hotspots recently.