ATLANTA -- CDC officials said expectant moms planning to visit any of 14 areas in the Caribbean and Central and South America should reconsider, in light of the surge in microcephalic infant births believed to stem from Zika virus infection, and to take steps to avoid mosquito bites if they choose to go anyway.
The same advice applies to women trying to become pregnant, the agency said late Friday.
Nations and territories named in the alert include: Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, and Puerto Rico.
"Further spread to other countries in the region is likely," the CDC said in a Health Alert Network announcement.
"Pregnant women in any trimester should consider postponing travel to the areas where Zika virus transmission is ongoing," the agency advised. It added that women who are or may potentially become pregnant who do travel to these regions "should talk to their doctor or other healthcare provider first and strictly follow steps to avoid mosquito bites during the trip."
Those steps include using insect repellents, staying covered when venturing outside, and using bed nets while sleeping if exposed to the outdoors.
Zika virus has been known since the 1940s and has gradually become endemic in areas of Africa, Asia, and the Pacific Islands. Only recently, however, has it become established in the Western Hemisphere.
It became of major public health concern last year when thousands of cases of microcephalic infant births were noted in northeastern Brazil, tied to Zika virus infection during pregnancy.
A causal mechanism has not yet been definitively established, but public health officials are now acting out of "an abundance of caution," as the CDC put it.
Symptoms of Zika infection include acute onset of fever, maculopapular rash, arthralgia, and/or conjunctivitis. Healthcare providers encountering patients with these symptoms following travel to affected areas should contact public health authorities as soon as possible. No commercial test is available for Zika virus, the CDC noted; testing is performed only by the CDC and a few state public health laboratories. There is also no specific treatment or vaccine.