The first case of female-to-male sexually transmitted Zika has been reported in NYC

The CDC has documented the first case of female-to-male sexually transmitted Zika in the United States.

According to a report released Friday, a woman travelled from a country with mosquito-transmitted Zika back to New York City. Upon return, she had condomless sex with a man. Over the next few days, her symptoms (fever, fatigue, muscle and joint pain, swelling, numbness and tingling) got worse, at which point she got her blood and urine tested. Those both tested positive for Zika.

A week after the partners had sex, the man started feeling similar symptoms (rash, joint pain, fever, and pink eye). The man — who reported that he hadn’t left the US for a year before his illness — got his blood and urine tested, but only the urine tested positive for Zika.

“The timing and sequence of events support female-to-male Zika virus transmission through condomless vaginal intercourse,” the CDC concluded. That might have happened because menstrual blood or vaginal fluids came into contact with the man. A study in the journal Lancet reported that Zika in the female genital tract could be detected longer than in urine or blood samples.

Zika, which is transmitted mainly by mosquitoes, has been spreading around the Americas over the last year, though local transmission has yet to be reported in the US. Sexually transmitted cases have also been more frequent than first expected, but up until now, most reports have been cases of Zika-infected men passing it to their partners.

Once infected with Zika, only about 20% of people ever show symptoms, which most commonly include fever, rash, joint pain, and red eyes. There is no vaccine or treatment available for the virus.

One reason Zika is troubling — especially in cases of sexual transmission — is because it can cause birth defects, including microcephaly (a condition where the baby’s head is abnormally small) in babies whose mothers have had Zika. Sexual transmission from women to their partners could also be troubling, because the virus has been linked to a neurological condition called Guillain-Barré syndrome, a temporary condition where the immune system attacks the body’s nervous system.

NOW WATCH: This animated map traces the shocking spread of Zika and where it could hit next

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