A case of Zika virus in Texas was transmitted from one person to another during sexual intercourse. This is the first known instance of transmission of the virus in the United States.
Zika is usually transmitted by mosquito bites; transmission through sexual contact would be alarming if the virus spreads in the United States. The U.S. cases of Zika that have been diagnosed before this were in people who had traveled to Central or South America or the Caribbean and become infected there. The virus has been reported in more than 30 countries.
Dallas County Health and Human Services said it received confirmation of the case from the U.S. Centers for Disease Control and Prevention. A patient who had traveled to Venezuela appears to have transmitted the virus to a sexual partner, who had not traveled to South American. However, the Texas Department of State Health Services is not saying that sexual transmission was certain, stating: "Case details are being evaluated, but the possibility of sexual transmission from an infected person to a non-infected person is likely in this case."
Dallas County authorities said there were no reports of Zika virus being transmitted by mosquitoes in the county.
Zika is linked to severe birth defects in thousands of babies in Brazil and is spreading so rapidly in the Americas that World Health Organization officials are worried that it could hit Africa and Asia as well. Babies born to mothers who contracted the virus during pregnancy have smaller than normal heads, a condition called microcephaly.
A CDC spokesman confirmed the results of a test for Zika infection but said local officials investigated the mode of transmission.
Previously, international health officials say there has been one case of possible person-to-person sexual transmission. But more evidence is needed to confirm sexual contact as a likely means of Zika transmission. Zika has been detected in human sperm.