Governor Rick Scott signed the order on Wednesday to cover Miami-Dade, Lee, Hillsborough, and Santa Rosa counties.
Florida health officials have confirmed that there have been nine cases of the mosquito-borne Zika virus in the state, all of which occurred in people who've traveled to Latin America and the Caribbean, where the virus has been spreading.
The disease, for which there is no vaccine and no specific cure, has been linked to a recent surge of birth defects in Brazil.
None of the cases in Florida have involved pregnant women, officials said.
The emergency order authorizes the state's agriculture department to take action to combat the problem, such as spraying against mosquitoes. It also directs the Florida Department of Health to make its own decisions about what's needed from the state and the Centers for Disease Control and Prevention.
"Although Florida's current nine Zika cases were travel-related, we have to ensure Florida is prepared and stays ahead of the spread of the Zika virus in our state," Scott said in a statement. "...We know that we must be prepared for the worst even as we hope for the best."
CBS News chief medical correspondent Dr. Jon LaPook, who is covering the Zika outbreak in Brazil, said, "I think it's an attempt to stay ahead of the problem by lowering the odds that Zika virus will enter the local mosquito population in Florida."
Zika virus is believed to stay in a person's bloodstream for about a week after they're infected, during which time a mosquito could bite them, pick up the virus, and then bite another person and transmit it to them.
The Zika virus has been found in over two dozen countries, mainly in Latin America and the Caribbean.
So far, at least 48 cases of Zika have been reported in the U.S. All but one of them occurred in travelers infected abroad. The CDC said yesterday that they have confirmed one case of the virus being transmitted sexually in the U.S. In that instance, someone who had recently traveled to Venezuela spread the virus to another person in the Dallas area.
Only about 1 in 5 people infected with Zika virus show symptoms of illness. Signs and symptoms of Zika may include a low-grade fever, rash, joint pain, reddening of the eyes, body aches, headache, eye pain, and vomiting. Illness is often mild and typically resolves within a week.
The real concern is for women who are pregnant, as it has been linked to microcephaly -- a condition in which a baby is born with an abnormally small head, which can lead to mental retardation.
South Florida hospitals are now asking pregnant women if they have traveled to areas known to have confirmed cases of the Zika virus during the admission process. Pregnant women are being advised not to travel to areas where the virus is present. If they do, they should consult with their doctor first.