Ten pregnant women tested positive with preliminary testing for Zika in Dallas County. The good news is they all contracted the virus outside of the United States.

Dallas County Health and Human Services (DCHHS) Director Zachary Thompson announced 10 pregnant women traveled to Zika hot spots and appear to have returned with the virus. Thompson spoke to the Dallas County Commissioners Court, the Dallas Morning News reported Tuesday.

Medical officials test locally to determine the exposure to the Zika virus and, in some cases, send samples to the CDC for confirmation. Breitbart Texas reported in May that the FDA had approved new test that provides early detection of the Zika virus.

“We’re tracking 10 pregnant women with possible Zika infection,” said Thompson. “But no confirmation has been made at this time. Testing was performed at the Dallas County Health and Human Services laboratory, and sent to CDC for additional testing.”

He added: “We don’t want a localized case.”

In April, an El Salvadorian pregnant woman, who resides in Houston, tested positive for Zika, Breitbart Texas’ Lana Shadwick reported.

To date, all cases originated from travel outside the U.S. to Zika infested regions or were transmitted through sexual contact with an infected person who traveled to predominantly Latin American countries where Zika runs rampant.

According to the Centers for Disease Control and Prevention (CDC), 234 pregnant women in the U.S. tested positive for Zika. Another 189 tested positive in U.S. territories. So far, three babies were born exhibiting Zika related birth defects.

Three other pregnancies ended in miscarriages and stillbirths, with evidence of suspected Zika related birth defects including microcephaly, calcium deposits in the brain indicating possible brain damage, excess fluid in the brain cavities and surrounding the brain, absent or poorly formed brain structures, abnormal eye development, or other problems resulting from brain damage affecting nerves, muscles and bones, such as clubfoot or inflexible joints, says the CDC.

For most who contract Zika, symptoms last up to a week and are mild. They include fever, rash, joint pain, and conjunctivitis. However, the virus has also been linked to serious health complications such as Guillain-Barré syndrome, an immune system disorder that causes severe joint and muscle pain.

Dallas County officials remain concerned over the possibility of local mosquitoes biting an infected patient, in turn, infecting the local mosquito population. This would trigger a “transmission cycle,” which Breitbart Texas’ Bob Price reported.

In February, Dr. Jeffrey Kahn, chief of pediatric infectious diseases for the University of Texas Southwestern Medical Center in Dallas and a director of infectious diseases at Children’s Medical Center voiced that such a “transmission cycle” could start in Texas. The Aedes aegypti mosquito which carries Zika is native to the state. Should local mosquitoes get infected with the virus, Kahn noted it would be “almost impossible to get the virus out of the population.”

On Tuesday, Thompson added: “It’s not if we’re going to have one but when we’re going to have one. And what impact that’s going to have on our residents, especially the fear among pregnant women.”

Local health officials previously confirmed nine Zika cases. None of the patients were pregnant. Most contracted the virus through mosquito bites while on travel to countries like Honduras, El Salvador, Guatemala, Jamaica, and Venezuela.

The largely mosquito-borne transmittable virus can also be contracted through sexual contact with an infected person. Breitbart Texas reported the first U.S. case of hetero-sexually transmitted Zika happened in Dallas County. So did the nation’s first homosexually transmitted case, as reported by Breitbart Texas.

Thompson told county commissioners Tuesday the nine cases since cleared up, according to the Dallas newspaper. The DCHHS director recommended those planning to visit a Zika affected country should speak to their doctors before traveling, including to places like Brazil, the site of the 2016 Summer Olympics.

Although there is no vaccine to prevent Zika, the FDA just green-lighted Inovio Pharmaceuticals and GeneOne Life Science, makers of the first DNA-based vaccine, to begin a first phase of clinical testing within weeks. Breitbart Texas reported Brazil and the University of Texas signed an agreement to develop a vaccine. Dallas labs and Houston medical institutions stand on the forefront of early Zika testing.

For now, prevention remains key. DCHHS official Dr. Christopher Perkins stressed “education and awareness” crucial in preventing Zika. “Patients are highly encouraged to follow prevention recommendations to avoid transmitting and spreading Zika virus.”

Thompson reiterated Tuesday prevention starts with wearing mosquito repellent “all day every day.” He suggested limiting time outdoors at night, reminded Dallasites to remove standing water, and to use condoms when having sex with someone who traveled abroad.

Dr. Patrick Ramsey, the South Texas vice chair of the American College of Obstetricians and Gynecologists, told the Morning News women should use mosquito repellent all the time; pregnant women, too. He called bug sprays safe for pregnant women to use.

Thompson noted the same Aedes aegypti mosquitoes that carry Zika transmit West Nile virus, a major concern to local health officials. Five mosquito pools tested positive for the virus so far this year, Thompson said. “We still feel that West Nile’s public enemy No. 1.”

Editor’s Note: This article has been updated with additional information.

Follow Merrill Hope, a member of the original Breitbart Texas team, on Twitter @OutOfTheBoxMom.