By Julie Steenhuysen

CHICAGO (Reuters) - The state of Florida, the first to report the arrival of Zika in the continental United States, has yet to invite a dedicated team of the federal government's disease hunters to assist with the investigation on the ground, health officials told Reuters.

Coordination with the U.S. Centers for Disease Control and Prevention since the state reported possible local Zika transmission on July 19 has been conducted largely at a distance, they said. That is surprising to some infectious disease experts, who say a less robust response could lead to a higher number of infections.

While Florida has a strong record of battling limited outbreaks of similar mosquito-borne viruses, including dengue and chikungunya, the risk of birth defects caused by Zika adds greater urgency to containing its spread with every available means, they say. Other states have quickly called in CDC teams to help track high-profile diseases.

"You only have a small window. This is the window" to prevent a small-scale outbreak from spreading, said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston, who expressed impatience with the pace of the Florida investigation.

Florida on Friday said that four cases of Zika in the state were likely caused by mosquito, the first sign that the virus is circulating locally, though it has yet to identify mosquitoes carrying the disease.

The current Zika outbreak was first detected last year in Brazil, where it has been linked to more than 1,700 cases of the birth defect microcephaly, and has since spread rapidly through the Americas.

Florida Governor Rick Scott said the state health department was working with the CDC as it continues its Zika investigation. CDC said it is closely coordinating with Florida officials who are leading the effort. Dr Marc Fischer, a CDC epidemiologist, has gone to Florida at the state's request.

But the state has not invited in the CDC's wider emergency response team of experts in epidemiology, risk communication, vector control and logistics, according to Florida health department spokeswoman Mara Gambineri.

In its plans to fight Zika nationwide, CDC stressed that such teams would help local officials track and contain the virus. Similar teams were sent to Utah earlier this month to solve how a person may have become infected while caring for a Zika-infected patient, before local officials went public with the case, and quickly joined an effort to contain an Ebola case in Dallas in 2014.

"Should we need additional assistance, we will reach out," Gambineri said in an email. She did not reply to questions about why the state decided not to bring in a CDC team.

CDC spokesman Tom Skinner said the agency has several teams ready for when states request help with Zika, including Florida.

"If invited, we've got a team ready to go," he said.



Florida health officials publicly disclosed the first case of suspected local transmission on July 19.

They have since been testing hundreds of area residents to identify other possible infections, in some cases knocking on doors asking people to provide urine samples, and studying local mosquito populations to see if they are carrying the virus.

The state has warned residents to protect themselves against mosquito bites, and distributed Zika prevention kits for pregnant women at local doctors' offices.

Michael Osterholm, an infectious disease expert from the University of Minnesota, said the two counties involved in the Florida probe – Miami-Dade County and Broward County - have extensive mosquito control experience. But he was surprised that the state had not yet sought CDC's help in quickly gathering information about where people were when they were bitten.

"When cases like this occur, it's critical that there be rapid epidemiological investigations to determine the likely location where the mosquito exposure occurred," Osterholm said. "Only with that can you identify the breeding sites and eliminate them."

As Zika's arrival in the United States loomed in recent months, Republican and Democratic leaders have blamed each other for holding up funding to fight it. President Barack Obama's administration asked Congress for $1.9 billion to fund a Zika response. Republican lawmakers proposed much smaller sums, and talks with their Democratic counterparts stalled before Congress adjourned for the summer.

Scott, a Republican, said on Friday he had asked top officials in the Obama administration, including CDC Director Tom Frieden, for more resources to fight Zika. He has allocated$26 million from the state's budget.

On July 20, the White House said that Obama had called the Florida governor to discuss the possibility that Zika was circulating in the state, and promised an extra $5.6 million in federal funding in addition to about $2 million provided by CDC. 

The statement praised Florida's record of responding to mosquito-borne outbreaks and its close coordination with federal partners, including the CDC.

"Florida does what Florida does," said one public health expert familiar with the investigation. "If I were health commissioner, I would have asked for their (CDC's) help immediately."

(Reporting by Julie Steenhuysen; Editing by Michele Gershberg and Bernard Orr)