10 pregnant women in Dallas showing signs of Zika virus

Ten pregnant women in Dallas, Texas, are showing symptoms of Zika virus infection, according to health officials there.

Dallas County Health and Human Services said Tuesday that there are nearly a dozen total cases in North Texas, CBS Dallas-Fort Worth reported, but none were contracted in the U.S.

Local cases are cause for concern. The virus can be spread if an infected person is bitten by a certain type of mosquito that then goes on to bite other people. That's the way the disease spread from Brazil throughout Latin America and the Caribbean over the past year. The same type of mosquito is found in parts of the southern United States.

The Centers for Disease Control and Prevention will not confirm any diagnosis publicly until after the babies are born. The federal health agency confirmed in April that the Zika virus can cause a birth defect called microcephaly -- an underdeveloped brain at birth. It's the first time in history a virus transmitted by mosquito bite has been found to cause birth defects.

"What we're learning is that they have a severe form of microcephaly that is oftentimes associated with other problems in the brain that can be seen on imaging or CT scan or MRI's, that makes us really concerned," said the CDC's Dr. Sonja Rasmussen at the time.

The CDC made the determination based on mounting evidence from many studies. Images released by researchers in Brazil, where the virus is widespread, show severe brain damage in babies with microcephaly.

The Zika virus is typically spread by mosquitos. According to the CDC, as of June 9, 234 pregnant women in the U.S. have come up positive in lab tests for evidence of Zika virus infection. As of June 15, a total of 756 cases of Zika have been reported across the country -- all in people who contracted it abroad or through sexual contact with someone who traveled abroad.

Earlier this year, Dallas County health officials reported the first case of the Zika virus transmitted through sex. Those two patients have both since fully recovered.

Most of the Texas cases have come from Harris County, which includes Houston.

According to the CDC, only about 1 in 5 people infected with Zika actually become ill. The most common symptoms include a fever, a rash, joint pain and red eyes. Other common symptoms include muscle pain and headaches. The symptoms often last for up to a week. A blood or urine test can confirm Zika infection.

There is no medication to prevent or treat the Zika virus at this time. Anyone who is infected should get rest, drink plenty of liquids and take acetaminophen to help with fever and pain. The virus rarely results in hospitalization or death, but it is a great concern for pregnant women because of the risk of birth defects.

The CDC's recommendation for pregnant women is to avoid travel to areas where Zika virus is spreading, and for their partners who have traveled there to abstain from sex or use latex condoms.

People who live in or travel to areas where Zika infection is a risk should take steps to avoid mosquito bites. Wear long sleeves and long pants, stay in places with air conditioning and screens on doors and windows, and use EPA-registered insect repellents -- applying sunscreen before mosquito repellent, the CDC says.