The Zika virus is primarily spread by mosquito bites, but emerging research on the sexual transmission of the virus suggests it’s a lot more common than previously thought. And it doesn’t have to be vaginal sex that transmits the disease.
In an op-ed published in the New England Journal of Medicine Thursday, doctors described their theory that a man traveling from Rio de Janeiro may have spread the virus to his partner through oral sex.
The 46-year-old man had suffered from fever, a rash and muscle pain on Feb. 7 while he was in Brazil, but the symptoms had disappeared by the time he arrived in France on Feb. 10. He then had unprotected sex seven times with his partner between Feb. 11 and 20, engaging in both vaginal and oral sex. However, his partner only had contact with his semen during oral sex, the doctors noted.
By Feb. 20, the 24-year-old partner, who had been living in Paris and had not traveled to a region with active Zika transmission, began to experience the same symptoms the man had experienced in Brazil. Her symptoms lasted for one week.
Both patients ended up testing positive for Zika virus. The woman had traces of the virus in her saliva and urine, but not in her vaginal fluid or blood. The man tested positive for the virus in his urine and semen, but not in his saliva or blood.
The medical results suggest that the man passed Zika virus to his partner via oral sex, although the researchers concede that they can’t rule out transmission via pre-ejaculate fluid during vaginal sex or saliva during "deep kissing."
Scientists have known since 2011 that Zika virus might be spread sexually. A researcher who got the disease in Senegal went back home to Colorado, where he had unprotected sex with his wife and then passed the disease on to her.
This initial case was later confirmed during the current Zika virus epidemic in Latin America after several transmissions in which travelers passed the virus to partners after returning home to countries without endemic Zika spread.
Ten countries have reported local Zika virus transmission even though their local mosquito populations don’t carry the disease, reported The New York Times -- an indication of sexual transmission. In the U.S., there have been 11 cases of sexually-transmitted Zika virus since the current epidemic started.
Because of this, the U.S. Centers for Disease Control and Prevention has recommended that men traveling in Zika-endemic countries use condoms for oral, vaginal or anal sex with their partners once they return home. This advice is especially urgent for couples who are pregnant, as a sexually-transmitted Zika virus presents extraordinary risk to the developing fetus, including miscarriage, stillbirth and microcephaly.