The first case of female-to-male sexual transmission of the Zika virus was reported in New York City on Friday.
According to the Centers for Disease Control and Prevention, the unidentified 20-year-old woman traveled to a country with an ongoing Zika pandemic. She had sex with her partner without a condom the day she returned home. The next day, she suffered from fever, fatigue, rash, and swelling of the extremities. Three days after, she decided to visit a doctor who took blood and urine samples. Tests showed she was infected with Zika virus.
A week later, her partner complained of the same symptoms and went to the same doctor. He tested positive for the virus on his urine sample. He told health investigators that he didn't travel outside the United States in the past year, and had no other sexual partners.
Investigators came to the conclusion that that the virus, either in his partner's vaginal fluids or menstrual blood, was transmitted to him.
"This case represents the first reported occurrence of female-to-male sexual transmission of Zika virus," the CDC report reads. "Ongoing surveillance is needed to determine the risk for transmission of Zika virus infection from a female to her sexual partners."
Zika is primarily caused by a virus transmitted by yellow fever mosquitoes, Aedes aegypti. It can cause birth defects including brain and skull deformity.
The CDC has also announced that its updating its guidelines because the current advice to prevent sexual transmission of Zika "is based on the assumption that transmission occurs from a male partner to a receptive partner."