So far, all known cases of sexually transmitted Zika have involved a man spreading it to a partner. The virus thrives in semen, and lives there longer than it does in blood, which is why experts recommend that men use condoms if they’ve been in areas where Zika is spreading—for six months if they’ve had symptoms, and eight weeks even if they haven’t.
Currently, the website of the Centers for Disease Control and Prevention states, “We don’t know if a woman with Zika can pass the virus to her partners, during vaginal or oral (mouth-to-vagina) sex.” But now there’s reason to suspect that women might be able to.
In a new case study published in The Lancet Infectious Diseases, doctors at Pointe à Pitre University Hospital, in Guadeloupe, treated a woman with Zika in May, and detected the virus in her genital tract. When she first came in, her blood tested positive for Zika, though her urine did not. Three days after the onset of her symptoms, doctors did a genital swab, a swab around the opening of the cervix, and also took a sample of cervical mucus. All three samples tested positive for Zika virus RNA. They did another round of tests 11 days after her symptoms started—of blood, urine, and cervical mucus—and while the blood and urine were clear, the virus was still in the mucus.