Sexually Transmitted Case of Zika Virus Found in US, Dallas Health Dept. Says

— -- The Zika virus has been sexually transmitted between two people in the U.S., according to a report by the Dallas County Health and Human Services Department.

A patient contracted the disease in Dallas County after having sexual contact with a person who was infected with the Zika virus in a country where Zika virus was present, the agency said today.

"Now that we know Zika virus can be transmitted through sex, this increases our awareness campaign in educating the public about protecting themselves and others," said Zachary Thompson, director of the Dallas County Health Department. "Next to abstinence, condoms are the best prevention method against any sexually transmitted infections."

The U.S. Centers for Disease Control and Prevention confirmed the finding in a statement to ABC News.

"CDC has confirmed through laboratory testing the first case of Zika virus infection in a non-traveler in the continental United States," in the current outbreak, a CDC spokeswoman told ABC News. "According to a Dallas County Health Department investigation, a person who recently traveled to an area with Zika virus transmission returned to the United States and developed Zika-like symptoms. The person later tested positive for Zika, along with their sexual partner, who had not traveled to the area."

Before this case in Texas, a researcher who was infected with Zika virus in Senegal in 2008 returned home to Colorado, and is believed to have infected his wife through sexual transmission, according to paper in the CDC's Emerging Infectious Diseases journal. That was long before the Zika virus outbreak reached the Americas.

The Zika virus is usually spread through mosquito bites, although in extremely rare cases it has been reported to be transmitted from mother and child during birth and through sexual contact and blood transfusions.

The Zika virus outbreak continues to spread, with at least 28 countries/territories identified as having current outbreaks of the virus, according to the U.S. Centers for Disease Control and Prevention.

The disease usually results in mild symptoms including fever and rash that end after about a week. However, it has been associated with a rise of a dangerous birth defect called microcephaly, where an infant has an abnormally small head, leading to potentially serious developmental delays.