Federal officials have begun door to door testing of citizens in Florida for the Zika virus.
Four people have tested positive in Miami-Dade and Broward counties, health officials admitted on Friday.
These are the first known cases of the virus being transmitted by mosquitoes in the continental United States.
“While no mosquitoes trapped tested positive for the Zika virus, the department believes these cases were likely transmitted through infected mosquitoes in this area,” according to a statement from the Florida Department of Health.
“As we anticipated, Zika is here,” Dr. Tom Frieden, director of the Centers for Disease Control and Prevention, said Friday, adding that “all the evidence we have seen indicates that this is mosquito-borne transmission that occurred several weeks ago.”
Frieden explained that confirming local mosquito-borne transmission of the virus is not as easy as confirming the virus in an individual by running a test. He also said that finding a Zika-carrying mosquito is like finding a needle in a haystack, and doing so is not necessary to confirm local mosquito transmission.
Officials believe the local transmission is confined to a small area north of downtown Miami within a single ZIP code.
However, local, state and federal health officials are continuing their investigation, which includes going door-to-door to ask residents for urine samples and other information in an effort to determine how many people may be infected. Additional cases are anticipated.
It is possible that someone could have Zika without knowing, since 80% of those infected have no symptoms. When symptoms occur, they can include fever, rash, joint pain and red eyes, and they can last from a few days to about a week.
There is no treatment or vaccine for Zika. None of these four unidentified patients, which include a woman and three men, has needed hospitalization.
To date, there have been 386 cases of Zika in the state of Florida, including 55 pregnant women. The counties with the highest number of cases are Miami-Dade with 99 and Broward with 55.