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Sex is causing Zika to spread more than scientists first realized

"Zika is a sexually transmitted disease now — we need to start thinking of it that way."
Carlos Varas, un responsable de la surveillance des moustiques à Miami-Dade, équipé d'un pulvérisateur de pesticide. (Joe Raedle/Getty Images)

The fight to stop the spread of Zika is going to take a bigger toll on people's sex lives than experts originally thought.

Men and women are now being advised to practice safe sex — or give it up altogether — for at least six months after they return from an area with active spread, according to updated guidelines published by the World Health Organization this week.

In places with active Zika cases, the new recommendations say men and women should have access to condoms and other contraceptives, as well as proper counseling about the risks of sexually transmitted Zika.


"Mounting evidence has shown that sexual transmission of Zika virus is possible and more common than previously assumed," the WHO states in the latest guidance update published this week. The UN health agency says sexually transmitted Zika is particularly a concern due to the link between Zika virus during pregnancy and severe birth defects like microcephaly.

While the small aedes aegypti mosquito gets most of the blame for outbreaks of Zika, WHO's latest guidelines are based on a growing pool of research and studies about sexual transmission of the virus.

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Zika was discovered in 1947, but it wasn't until 2011 that studies began highlighting the possibility that the virus could spread through sexual activity. At least 11 countries have since reported sexually transmitted Zika cases. Last year's unprecedented outbreak in Brazil, which was linked to an increase in babies born with microcephaly, ushered in a host of new research.

Back in June when the WHO made the last update to its interim guidelines, experts believed Zika could remain in semen for about eight weeks. At the time, safe sex recommendations for preventing transmission were only directed at men.

Since then, however, research indicates the virus sticks around for at least 24 weeks and that it can be transmitted from women to men.

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A recent report published by the US Centers for Disease Control and Prevention also detailed the first documented case of a woman who contracted the Zika virus through sex with a male partner who did not have any signs of infection. This validated concerns that the virus can be transmitted during sex, even if someone is not showing signs of Zika infection.

According to Dr. Benjamin Neuman, a virologist at Texas A&M University-Texarkana, looking at the Zika virus as more than just a mosquito-borne disease is the new normal.

"Zika is a sexually transmitted disease now — we need to start thinking of it that way," Neuman said.