Florida officials and federal public health experts are keeping a careful eye on the mosquito population in Miami ahead of what they fear will be a breakout year for Zika, a virus that has already infected more than 5,100 people in the United States.

The Sunshine State is ground zero for transmissions of the mosquito-borne virus that happen on American soil. While the vast majority of people infected with Zika caught it while traveling abroad, all but six of the 222 confirmed cases acquired within the United States have been in Florida. The other six cases were acquired around Brownsville, Texas.

Florida Gov. Rick Scott (R) visited Miami-Dade County officials on Monday to evaluate preparations in the weeks and months leading up to Florida’s balmy rainy season, when mosquito populations boom. The Centers for Disease Control and Prevention, meanwhile, has an incident manager coordinating the federal response from the agency’s Atlanta headquarters. 

{mosads}The Zika virus first made landfall in the United States last year in the Miami-Dade area, where infections were traced to four neighborhoods in Hialeah and Miami Beach. Local, state and federal officials sent hundreds of people to the city to monitor and contain the mosquito-borne virus, which died down as the winter months took hold. 

“We learned a lot last year. The Florida experience in particular was very helpful in learning how to deal with local transmission,” said Denise Jamieson, chief of the CDC’s Women’s Health and Fertility Branch and the official in charge of the CDC’s Zika response. “We learned a lot about how to designate and communicate about areas of risk.” 

Preparations for this year’s mosquito season have involved a dramatic expansion of the Miami-Dade County Public Works and Waste Management Department. Gayle Love, a senior division director at the department, said her agency is in the process of hiring 42 new employees, including a medical entomologist. 

“After we responded to the Zika challenge, we just kept going,” Love said in an interview. “After last year, we saw the level of intensity that was required for our response.”

The department last year hired 200 temporary employees and contractors to spray chemicals meant to kill mosquitoes around the Miami-Dade area. This year, they will hire more contractors, and the agency is already monitoring 130 traps set up throughout the county. If those contractors find any more than 10 female Aedes aegypti mosquitoes in a trap, they will spray the area to contain the population.

“Mosquito season has peak activity in summer and rainy months,” Love said. But now, she added: “We consider it a year-round problem.”

Public health officials say they expect Zika to spread more broadly in Florida this year, where only a small number of cases occurred last year. There are likely to be fewer cases in Puerto Rico after the island was hit hard last year, when more than 38,000 people were infected. Once someone contracts the Zika virus, they are immune from contracting it again. 

“We expect fewer cases in places like Puerto Rico because a proportion of the population was infected and is less susceptible,” Jamieson said. 

Miami officials said fighting the Zika outbreak had already cost the county more than $23 million. The state of Florida has reimbursed the county for $18 million in costs. The Florida Department of Health said last week it had tested more than 13,000 people for the Zika virus throughout the state.

State legislators added $2.6 million in funding for mosquito control programs around Florida. Those programs are seeking another $3.8 million in state funding. Sens. Marco Rubio (R-Fla.) and Bill Nelson (D-Fla.) have introduced federal legislation to give small businesses access to federal disaster relief money if they are impacted by Zika’s spread. The bill would also fund a Department of Health and Human Services program to respond to public health emergencies. 

The CDC and Florida officials say they will work to let pregnant women know of any Zika hotspots that pop up, like the four that emerged last year. And CDC is working to speed laboratory testing times, while adding capacity to registries that track those already infected by the virus. Those registries are mostly populated by people infected abroad.

So far this year, Miami-Dade officials have identified 29 new Zika cases. Officials said only two of those cases were contracted through local transmission in Florida, both of whom were likely infected last year.