CDC Director Dr. Tom Frieden told CNBC on Tuesday that pregnant women throughout the South should protect themselves against mosquito bites because of the risk of the Zika virus.
Zika is primarily transmitted through infected Aedes species of mosquitoes, according to the website for the Centers for Disease Control and Prevention.
"Until we're done with mosquito season, anywhere in the U.S. where this mosquito is present, there is a potential risk," Frieden said on "Squawk Box."
But Frieden stressed, by all accounts so far, the only place in the nation where the virus is spreading locally is in Miami's Wynwood arts district, a neighborhood known for its galleries, restaurants, and boutiques.
In a highly unusual travel warning, health officials on Monday advised pregnant women to avoid that part of Miami, citing Zika cases they strongly believe were caused by local mosquitoes.
Ten more cases were announced Monday, in addition the four from last week.
Pregnant women are most at risk because infections can cause the microcephaly and other severe brain abnormalities in their babies.
Symptoms of Zika can include include fever, rash, joint pain and red eyes. The virus is often so mild that most people don't know they are infected.
Zika acts like no other mosquito-borne disease, spreading through sexual contact and causing birth defects, Frieden said.
More than 1,650 cases of Zika have been reported in the United States. Nearly all have been the result of travel to a Zika-stricken country or sex with someone who was infected abroad.
Florida Gov. Rick Scott has asked for a CDC emergency team to help the state combat Zika, which has been sweeping Latin America and the Caribbean.