A county in Texas on Tuesday reported a case of Zika virus being sexually transmitted, raising new concerns about the spread of a mosquito-borne virus linked to birth defects.
Dallas County Health and Human Services said the patient was infected by a person who had traveled to Venezuela, but declined to identify the gender of the traveler or whether a pregnant woman was involved.
The county "has received confirmation from the Centers for Disease Control and Prevention (CDC) of the first Zika virus case acquired through sexual transmission in Dallas County in 2016," said a statement.
"The patient was infected with the virus after having sexual contact with an ill individual who returned from a country where Zika virus is present," it added.
The "confirmed case did not travel."
A spokesman for the CDC said the federal agency did not investigate the mode of transmission, but did confirm the infection.
Last week the CDC said it was aware of one reported case of sexual transmission of Zika and one case of the virus being present in a man's semen after it disappeared from his blood.
CDC principal deputy director Anne Schuchat told reporters on January 28 that the federal agency was aware of "one reported case of Zika virus through possible sexual transmission."
That case, according to a report in the New York Times, involved a US biologist who was infected in 2008 with Zika while in Senegal collecting mosquitoes for a malaria study. He apparently infected his wife upon his return.
"In another case, Zika virus was found in semen about two weeks after a man had symptoms with Zika virus infection, so that sort of gives you the biologic plausibility of spread," Schuchat added.
The World Health Organization has declared an international health emergency over Zika and warned that the virus may cause up to four million cases in the Americas.
The virus is "strongly suspected" of causing a surge in microcephaly cases -- in which babies are born with unusually small heads -- in Brazil since last year, but cause and effect has not yet been scientifically proven.
Researchers believe that if a pregnant women is bitten by an infected mosquito, particularly in the first trimester, she faces a higher risk of having a child with birth defects.
"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, DCHHS director.
"Next to abstinence, condoms are the best prevention method against any sexually transmitted infections."