Zika cases in Miami area likely result of local mosquitoes

The first cases of locally transmitted Zika virus in the continental United States have likely occurred in Florida.

State health officials believe four patients in the Miami area contracted the virus several weeks ago after they were bitten by infected Aedes aegypti mosquitoes in the city.

“As we have anticipated, Zika is now here,” CDC Director Thomas R. Frieden, MD, MPH, said today during a teleconference with reporters.

During an earlier news conference, Florida Gov. Rick Scott said there have been no other cases of local transmission reported in the state, and that “all these cases are located in South Florida.”

A. aegyptimosquitoes do not travel far in their lifetimes, and the Florida Department of Health (DOH) believes transmission occurred in a small area north of downtown Miami encompassing the neighborhood of Wynwood. The approximately 1 square mile area is the only place in the state where the DOH is testing for local transmission of Zika, Scott said. So far, testing has not turned up any mosquitoes carrying the virus, but the DOH has organized increased spraying and mosquito abatement measures in the area.

“It’s not expected that we would find infected mosquitoes even if there is spread in that area,” Frieden said.

Until now, each of the more than 1,600 cases of Zika virus in the continental U.S. were acquired outside of the country. The CDC has warned against traveling to other countries where local transmission of Zika was occurring, but Frieden said it would not implement the same warning for Miami — even for pregnant women — unless such cases continue to occur.

“That would be a very different situation,” he said.

Of the patients, three are male and one is female, Scott said. Two live in Miami-Dade County and two in neighboring Broward County. None has exhibited symptoms that require hospitalization, Scott said.

“While no mosquito traps have tested positive for Zika virus,” Scott said, “the department of health is aggressively testing people in the affected area to ensure there are no other cases of this virus.” Frieden said anyone else who wants to be tested should tell their doctor, who can contact the local health department.

Zika virus is primarily spread by mosquitoes, but also can be sexually transmitted by men and women. Infection during pregnancy can cause grave fetal outcomes such as microcephaly.

On July 28, the FDA ordered facilities in Miami-Dade and Broward counties to stop taking blood donations amid the DOH’s investigation into the locally transmitted Zika cases. In a statement, Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, called it a “prudent measure” to assure the safety of blood and blood products until they can be properly screened.

Peter Marks

Meanwhile, Zika prevention kits and repellent are being distributed at local obstetrician-gynecology offices and DOH locations in both counties, the department said.

As of July 28, there were 383 confirmed cases of travel-related Zika virus infection in Florida, including 55 involving pregnant women, the department said.

Scott said the state has the capacity to test 6,609 people for active Zika virus and 2,059 people for Zika antibodies. He said 2,329 people have been tested in Florida. More tests can be requested from the CDC as needed, the governor said. – by Gerard Gallagher

Disclosures: Scott is the governor of Florida, and Marks works for the FDA.