Florida authorities on Friday reported the first sign of local Zika transmission in the continental United States, concluding that mosquitoes likely infected four people with the virus that can cause a rare but serious birth defect.
Governor Rick Scott said the state believed active transmission of the virus was occurring within an area of Miami about the size of 2.6 square kilometres. Testing showed that one woman and three men had been infected, Scott said.
While health officials have yet to identify mosquitoes carrying the virus, the state has ruled out other means of transmission, including travel to another country with a Zika outbreak, and sexual contact.
"This means Florida has become the first state in the nation to have local transmission of the Zika virus," Scott said at a press conference.
Zika appears to pose the greatest risk when it infects pregnant women, given its ability to cause microcephaly in babies, a condition defined by small head size that can lead to developmental problems. The current outbreak was first detected in Brazil last year and has since spread rapidly through the Americas.
Florida Surgeon General Celeste Philip said that health officials are not advising pregnant women to move out of the suspected transmission area.
"We do not believe there will be ongoing transmission," Philip said at a press conference in Orlando, citing daily efforts to control the mosquito population in the area.
The local health department is searching for other potential infections, with more than 2,300 people tested so far in the state, is ramping up mosquito control programs and is distributing Zika protection kits to pregnant women at their doctors' offices, Florida officials said.
Federal authorities have already begun to treat the Florida cases as a sign of local transmission. On Wednesday, the US Food and Drug Administration ordered blood banks in Florida's densely populated Miami-Dade County and Broward County to stop collecting blood until they can test each unit or incorporate technologies that can kill blood pathogens.
Residents in the trendy Miami neighbourhood thought to harbour Zika said the local spread of the virus had been inevitable, given the large numbers of tourists from other countries with outbreaks.
Damian Jose Delgado, a 35-year-old father of two, said news of Zika's arrival would make him think twice about expanding his family.
"I think I might be done having kids," Delgado said.
Federal scientists kept at arm's length
The state of Florida is 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.
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.
Coordination with the US 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.
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.
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.
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.