Update on August 2, 2016
Since this report, the Florida Department of Health has now identified 10 more individuals with locally transmitted Zika virus disease, up from 4 cases a few days ago. In response, CDC is now issuing a travel warning for pregnant women to avoid a small section of Miami-Dade County, just north of downtown Miami, where officials believe the transmissions are occurring.
In addition, CDC recommends that pregnant women and their partners living in the area should consistently follow steps to prevent mosquito bites and sexual transmission of Zika virus disease. Pregnant women who were in the affected area on or after June 15 should talk to their health care provider and be tested for the virus. Pregnant women with no Zika virus disease symptoms who live in or often travel to the affected area should be tested for the virus in the first and second trimesters of pregnancy.
Initial report on August 1, 2016
Four individuals in Florida who have Zika virus disease are said to have contracted the disease from local mosquitos, indicating to health officials that Zika virus disease is now in the United States.
“All the evidence we've seen indicates that this is mosquito-borne transmission that occurred several weeks ago,” said CDC Director Tom Frieden, MD, MPH, during a call with reporters.
“Zika is now present in the continental U.S.,” Frieden said.
Florida officials also confirmed the cases.
Frieden said four individuals, three men and one woman, likely contracted Zika virus disease in early July. They showed symptoms about 1 week later.
As officials continue their investigation, they are concentrating on one small area several blocks north of downtown Miami where the individuals work, each in nonrelated establishments.
“With Zika, it’s a very focal disease,” said Frieden. “The Aedes aegypti mosquito does not travel more than about 150 meters in its lifetime—and often quite a bit less than that.” The A. aegypti mosquito is the species that carries Zika virus disease.
Compared to the West Nile virus, where circulation can cover a large area, mosquito control is different for Zika virus disease, according to Frieden.
CDC and the Florida Department of Health have already been conducting aggressive mosquito control activities and continue to do so. They also continue to issue precautions, especially for pregnant women. CDC has linked Zika virus disease to microcephaly, a birth defect that causes babies to be born with a shrunken head and incomplete brain development.
“It’s particularly important for pregnant women to avoid mosquito bites in all areas where the A. aegypti mosquito is present by using DEET, wearing long sleeves, and avoiding mosquito bites to protect themselves,” said Frieden.
Frieden said people living anywhere where the A. aegypti mosquito is present should protect themselves against mosquito bites by applying insect repellent, wearing long-sleeve shirts and long pants, removing standing water where mosquitos can lay eggs, making sure windows have screens, and staying in air-conditioned spaces when available.
The virus can also be transmitted sexually.
Until now, almost all Zika virus disease cases in the United States had been travel-related. More than 380 of the 1,650 cases CDC is monitoring are in Florida.
CDC was expecting local transmission of Zika virus disease at some point this summer as temperatures rise along the Gulf Coast. The area is a breeding ground for the A. aegypti mosquito.
However, at this time, health officials are not issuing a travel ban for Florida or calling for limited travel to the area.
“If, however, we were to see continuing spread in this area or somewhere else, or explosive spread, then we would absolutely issue travel guidance. That's not the situation that we're in today, but we will reassess that every single day,” said Frieden.