(CNN) Pregnant women who have "lived in, traveled to, or had unprotected sex with someone who lived in or traveled to Miami-Dade County" since August 1 should be tested for the Zika virus, the Centers for Disease Control and Prevention said Wednesday.
"Our guidance today strengthens our travel advice and testing recommendations for pregnant women, to further prevent the spread of the infection among those most vulnerable," Dr. Lyle Petersen, director of the CDC's Division of Vector-Borne Diseases, said in a statement.
The updated recommendations for Miami-Dade County come in response to last week's announcement by Florida Gov. Rick Scott that local transmission of the virus was confirmed in Miami's Little River neighborhood -- the third Miami neighborhood where local transmission or non-travel related cases have been confirmed.
Zika can be especially devastating for pregnant women because the infection can cause the devastating birth defect microcephaly and other neurological deficits. It can also cause miscarriage and stillborn births.
Florida officials have said Zika was only being actively transmitted in two Miami neighborhoods: the 1-square-mile area in Little River and a 4.5-square mile stretch of Miami Beach. Pregnant women should avoid travel to those areas, the CDC reiterated, echoing previous advice.
The CDC is now designating active transmission areas by the color red and cautionary areas, where local transmission is considered to be at risk, with the color yellow. Pregnant women should consider postponing travel to the rest of Miami-Dade, which are considered yellow areas, the agency said.
In July, the CDC had confirmed the first local transmission in the continental US in the Wynwood neighborhood of Miami. The agency later lifted a warning for pregnant women to steer clear of Wynwood after massive mosquito control efforts successfully stopped local transmission of the virus there.
The CDC said pregnant women who live in, have traveled to or had unprotected sex with anyone who lived in or traveled to the 4.5-square mile area of Miami Beach since July 14 should be tested for the virus.
The CDC has designated all of Miami-Dade County as an area where there has been local transmission but not at the same "intensity" as in the areas where local transmission has been confirmed.
In August, the CDC first advised pregnant women to consider postponing travel to all areas of Miami-Dade because of the virus.
"Zika continues to pose a threat to pregnant women living in or traveling to Miami-Dade County," Petersen said.
To date, there have been 184 locally transmitted cases of the virus in Florida, including 19 nonresidents who became infected while visiting Florida, according to state health department figures. In addition, there are nearly 800 travel-related cases in Florida, figures show.
On Thursday, U.S. Health and Human Services Secretary Sylvia Burwell is expected to travel to Cuba for the so-called Cuba Zika Summit, a regional meeting on surveillance and control strategies for Zika and other arborviruses.