Several doctors have contacted the Los Angeles County Public Health Department asking for blood tests for patients exhibiting symptoms of the Zika virus, the department said Friday.

A pregnant woman was among those patients.

The testing will be performed by the federal Centers for Disease Control (CDC) in Atlanta, which so far has confirmed 12 cases nationwide. California at this point is not among the handful of states that have the materials to perform the test to identify the virus, which was unseen in the United States until recently.

Outbreaks of the mosquito-borned virus have been reported in Africa, Southeast Asia, the Pacific Islands and Central and South America.

Health officials are investigating a link between infections and subsequent birth defects, and the CDC Friday added more nations and territories to its warning for travel that already includes much of the Caribbean and Latin America, including Mexico. The warning applies to two U.S. territories, Puerto Rico and Samoa.

The travel warning also extends to Brazil, which will host the Olympic Games this summer in Rio de Janeiro.

The CDC advises those who must travel to the locations to cover exposed skin with long sleeves and pants, and to use mosquito repellant. The warning is intended especially for expectant mothers, as there are indictions the virus can pass throught the placenta to infect the fetus.

Evidence indicates a link to microcephaly, a condition in which the brain and skull do not develop to full size. A baby born in Hawaii with microcephaly tested positive for Zika.

The CDC is recommending consideration of ultrasound examination of pregnant women who suspect they may have been exposed to the virus.

Symptoms in adults are described as cold or flu-like and are usually mild. Four of out of five adults who become infected with Zika do not develop noticeable symptoms.

None of the possible southern California cases has been confirmed.

Some five thousand physicians in Los Angeles case have already been contacted by Public Health as part of ithe Zika surveillance program being established, said Ben Schwartz, MD, deputy director for the acute communicable diseases control program. Zika is now considered "officially reportable as an unusual disease," Dr. Schwartz stated.

Originally a strictly tropical disease, Zika is carried by mosquitos only of the genus Aedes. There is a known Aedes population in Los Angeles County, but no evidence any have been infected with Zika, Dr. Schwartz said. Returning travelers suspected of being infected with Zika are asked to stay indoors to reduce risk of being bitten by a mosquito, which could in turn be infected and become a carrier.