Four cases of Zika virus in Florida are likely the first transmitted locally by mosquitoes in the United States, officials said Friday, marking a new phase in the fast-growing pandemic.
Until now, more than 1,600 cases of Zika, which can cause birth defects, have been recorded in the mainland United States but most were brought in by people who had become infected while traveling, with a smaller number transmitted by sexual contact.
"As we have anticipated, Zika is now here," said Tom Frieden, chief of the US Centers for Disease Control and Prevention (CDC), speaking to reporters in a conference call.
The Florida Department of Health said that over the past two weeks, investigators have determined "a high likelihood exists" that four suspected non-travel cases in Miami-Dade and Broward County "are the result of local transmission."
The department "believes that active transmission of the Zika virus is occurring in one small area in Miami-Dade County, just north of downtown," it added.
The area is a popular restaurant and arts district known as Wynwood.
Frieden said officials had no immediate plans to limit travel to the area.
— CDC (@CDCgov) July 29, 2016
However, Florida has yet to invite a dedicated team of the CDC to assist with the investigation on the ground, health officials told Reuters.
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 Governor Rick Scott said the state health department has been cooperating 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 Florida health department spokeswoman Mara Gambineri said that the state still has not invited in CDC's wider emergency response team of experts in epidemiology, risk communication, vector control and logistics.
"Should we need additional assistance, we will reach out," Gambineri said in an email.
CDC spokesman Tom Skinner said the agency is always ready to assist states for with Zika, including Florida.
"If invited, we've got a team ready to go," he said.
CDC provides advice on building a Zika virus prevention kit for people who live in states that Zika is spread.
— Florida Dept. Health (@HealthyFla)