Health officials have identified what they suspect to be the first female-to-male sexual transmission of the Zika virus, in a young woman in New York and her partner.
The woman, in her 20s, had returned to the city from travel to an area with active Zika transmission and engaged in condomless sex with her partner, according to a report Friday from the Centers for Disease Control and Prevention. The next day, she felt symptoms including fever, rash and muscle pain. She subsequently tested positive for Zika.
A week later, her partner experienced similar symptoms, and two days later, the Zika virus was detected in his urine, the CDC said. He reported no other recent sexual partners or mosquito bites in the preceding week, and no travel outside the U.S. for the previous year.
"This case represents the first reported occurrence of female-to-male sexual transmission of Zika virus," the CDC said. "Ongoing surveillance is needed to determine the risk for transmission of Zika virus infection from a female to her sexual partners."
It's been known that Zika can be transmitted from male sexual partners; for that reason, the CDC recommends pregnant women whose male partners have been in areas with Zika virus use condoms or abstain from sex during pregnancy.
The continental U.S. currently has no transmission of Zika through mosquitoes, the main source of the virus's spread. Of the total 1,306 cases of Zika reported in U.S. states, as of Wednesday, 14 have been sexually transmitted. Almost all the cases were travel-associated. However, in U.S. territories, there have been 2,916 cases of Zika, with nearly all of those have been locally acquired.
In New York City, 310 cases have been reported as of Wednesday, and in all of these cases the virus was contracted by visiting other countries.
The discovery of a new potential form of transmission, from women to their sexual partners, underscores what public health officials continually warn about Zika: that the more they learn about the virus, the more concerned they become.
"Zika is both unprecedented and tragic," CDC Director Tom Frieden said Wednesday at a hearing of the Senate Foreign Relations Committee. It's "the first time we've identified a mosquito-borne disease that is sexually transmitted."
Zika is most dangerous for pregnant women because it's been proven to cause birth defects including microcephaly and other brain defects.
Public health officials have been pleading with Congress to provide funding for Zika efforts, including development of vaccines and better diagnostics, but Democrats and Republicans failed to reach a compromise before leaving for summer recess this week.
In the hearing Wednesday, Sen. Marco Rubio called the "inaction" on Zika funding "simply inexcusable."
"It's taken far too long already," Rubio said.