Federal health officials on Monday advised pregnant women to avoid a Miami neighborhood — marking the first time the Centers for Disease Control and Prevention has warned against travel to any area within the continental United States — as a Zika outbreak in South Florida has led to 10 more local cases spread by mosquitoes.
The advisory extends to all expectant mothers, and women planning on becoming pregnant who have traveled to a one-square-mile area north of downtown Miami on or after June 15, said CDC Director Tom Frieden.
Pregnant women and their partners who live in the area are advised to take steps to avoid mosquito bites, such as using insect repellant with DEET and long sleeves and pants, and to avoid sexual transmission of Zika. Frieden also advised that all expectant mothers who have traveled to the area in recent weeks be tested for the virus.
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Perhaps most troubling, Frieden said, is that extensive spraying of insecticides in the area over the past several weeks has not reduced the local population of mosquitoes capable of transmitting Zika virus.
“It’s possible that the mosquitoes there are resistant to the insecticide that’s been used,” Frieden said. “It’s possible that there may be what we call cryptic breeding places. ... This is a very difficult mosquito to control, particularly in a complex urban environment.”
Friden said “there are undoubtedly more infections” in South Florida because only one in five people infected with Zika show symptoms, but he tempered his statement by noting that the Aedes aegypti species of mosquito most capable of transmitting the virus typically does not travel more than 150 meters in its lifetime.
“Nothing that we've seen indicates widespread transmission,” he said, “but it's certainly possible there could be sustained transmission in small areas.”
Among the 10 new local Zika cases reported on Monday, six are asymptomatic and were identified from the door-to-door community survey that the state’s health department is conducting. In total, Florida has reported 14 local Zika cases — 12 in Miami-Dade and two in Broward — including two women and 12 men.
In response to the new Zika infections, and the four cases identified last week as the nation’s first locally transmitted episodes, Florida Gov. Rick Scott called on the CDC to dispatch an emergency response team to Miami to help with the state health department’s ongoing investigations.
“Florida has a proven track record of success when it comes to managing similar mosquito-borne viruses,” Scott said in a written statement. “We will continue to keep our residents and visitors safe utilizing constant surveillance and aggressive strategies, such as increased mosquito spraying, that have allowed our state to fight similar viruses.”
The area, identified by Florida health officials, touches on the Wynwood, Midtown and Design District neighborhoods in Miami, popular with tourists. The area is bordered by Northwest Fifth Avenue to the west, U.S. 1 (Biscayne Boulevard) to the east, Northwest/Northeast 38th Street to the north, and Northwest/Northeast 20th Street to the south.
Frieden said that 12 of Florida’s 14 local Zika cases were transmitted within a 150-meter area surrounding an unidentified “workplace” likely at the center of the designated zone. The neighborhood remains the only area of Florida where the health department has confirmed ongoing local transmissions of Zika.
Asymptomatic men and women who have traveled to the Miami neighborhood in that time frame should wait at least eight weeks before trying for pregnancy, said Denise J. Jamieson, a physician and expert on pregnancy and birth defects with the CDC’s Zika response team. Symptomatic men with Zika should wait six months.
All residents of the area were advised to repair and use screens on windows and doors, and to remove all containers with standing water that may act as artificial mosquito breeding sites.
Florida health officials and local mosquito control workers have been inspecting and spraying the area since the first case was diagnosed several weeks ago. They also have been trapping and testing mosquitoes in Miami-Dade and Broward, where the state’s health department has reported two cases of Zika spread by local mosquitoes.
While some have criticized Scott for failing to ask the CDC to send an emergency response team prior to Monday, the federal agency and the White House have praised Florida’s aggressiveness in responding to mosquito borne-diseases in the past.
Frieden said on Monday that two members of the CDC’s emergency response team arrived in Florida last week, including a medical epidemiologist, Marc Fischer, and that three more would arrive on Monday and another three on Tuesday.
“We’ve had very close coordination, collaboration with Florida from the beginning of this,” Frieden said, adding that he has spoken almost daily with State Surgeon General Celeste Philip, and that experts from the CDC and Florida’s health department have been in contact, too.
“This just steps it up to the next level,” Frieden said of dispatching the eight-member team to Miami.
According to the CDC’s Zika response plan, the emergency team includes epidemiological experts in arboviruses, pregnancy and birth defects, as well as mosquito control experts and communications teams. When the CDC teams are deployed, the number of people included and their tasks all depend on the needs of the local jurisdiction, according to CDC guidance.
Florida and the CDC have long anticipated that Zika would begin to spread locally in Miami and other cities in the South, just like they saw with chikungunya and dengue fever and other mosquito-borne diseases. Despite thousands of imported cases of chikungunya virus, the CDC reported only 12 locally transmitted cases of the disease in Florida in 2014.
But Zika is different, not just because the virus can cause birth defects but because it is also sexually transmitted, and may be even more infectious from person to person than scientists know, as a mystery case currently under investigation by the CDC in Utah makes clear.
:What we know about Zika is scary,” Frieden said, noting that Zika is the first time scientists have seen a devastating birth defect like microcephaly resulting from a mosquito-borne disease, even among asymptomatic women.
“What we don't know is more unsettling,” he added, explaining that scientists have little research on the long-term effects of congenital Zika virus on children. “This may not become apparent for months or years,” he said.
Florida reported the state’s first baby born with Zika-related microcephaly in June. A total of 55 pregnant women statewide have been confirmed to have acquired the disease this year.
In the continental United States, a total of 1,657 Zika cases have been reported in 46 states — except Alaska, Idaho, Wyoming and South Dakota — as of July 27, according to the CDC. Florida has confirmed 386 Zika cases this year, not including the 14 local cases.
The Florida Department of Health has conducted testing for the Zika virus on more than 2,300 people statewide. Since DOH began its investigation into possible local transmissions of Zika on July 7, more than 200 people in Miami-Dade and Broward counties have been tested for the virus. They all live or work near the people already confirmed to have acquired Zika from local mosquitoes.
Frieden said it is likely but not possible to determine with science that the first local transmission involved a local mosquito biting someone who had contracted Zika while traveling abroad, and that insect then spreading the virus to others in the area.
“It’s unlikely we’ll ever know who brought it in and where they brought it in from,” he said, adding that international travel will continue to introduce new, asymptomatic people with Zika virus to South Florida and the rest of the continental United States.
“Everyone returning [from areas with ongoing Zika transmission] should use repellant for three weeks to protect their family in case a mosquito bites them and gets infected,” he said.
Zika cases reported in Florida as of Aug. 1
Number of Cases
Total cases not involving pregnant women
Cases involving pregnant women regardless of symptoms*
* Counties of pregnant women not disclosed.
** Does not included suspected cases of local transmission.
Source: Florida Department of Health