The Centers for Disease Control and Prevention (CDC) has warned women to wait eight weeks after visiting Zika-impacted Miami neighborhoods before trying to get pregnant in order to avoid potential birth defects like microcephaly. But now, the World Health Organization (WHO) is suggesting that women should wait over three times that long.
“Men and women returning from areas where transmission of Zika virus is known to occur should adopt safer sex practices or consider abstinence for at least six months upon return to prevent Zika virus infection through sexual transmission,” WHO announced in interim guidelines published Tuesday.
The WHO also specifically advises “couples or women planning a pregnancy” to “wait at least six months before trying to conceive to ensure that possible Zika virus infection has cleared.”
International media outlets quickly circulated the new WHO guidelines but many did not report a footnote which clarified that the “recommendation on adoption of safer sex practices or considering abstinence for six months is a conservative measure.” Many U.S.-based outlets, too, either omitted or did not notice that detail, either.
So far, the footnote states, sexual transmission of the Zika virus “has not been reported after 41 days of symptom onset.”
That doesn’t mean that the six-month recommendation is unfounded, especially given emerging research on the months-long persistence of the Zika virus in semen. As researchers uncover more knowledge about the effects of Zika seemingly by the day, many men and women may wish to follow the “conservative” estimate.
But for women especially, the current disconnect between the WHO interim guidelines and the CDC guidance is a potential point of confusion.
On May 30, as CNN reported, the WHO issued recommendations that were more closely aligned with the CDC’s current guidance: men and women should wait eight weeks to conceive after traveling to an area where there is local transmission of the Zika virus while men displaying symptoms should wait a full six months.
But now, the WHO’s new six-month guideline for safer sex or abstinence applies unilaterally to both men and women regardless of symptoms.
What changed? For one, a July report in The Lancet—cited by WHO in the new interim guidelines—found the Zika virus lingering in a 27-year-old woman’s cervical mucus even after her blood and urine tests came up negative. It should be noted, however, that the Lancet article only reported the woman’s test results for 11 days after symptom onset and the researchers could not state how long the virus could remain in cervical mucus.
“The duration of Zika virus persistence in the female genital tract and its clearance after the disappearance of the symptoms are unknown,” the report noted.
WHO spokesman Daniel Epstein did not immediately respond to a request for comment as to why women were now specifically included in the six-month guidelines.
“WHO reviewed published evidence including 17 studies or reports on sexual transmission of Zika virus and eight studies on the presence of Zika virus in semen, and consulted with different experts,” Epstein explained to The Daily Beast.
These studies and reports document transmission of the Zika virus from asymptomatic Zika-infected men to women and from a symptomatic woman to a male partner. They also include recent research that sheds new light on the persistence of the virus in semen.
To date, the Zika virus has not been successfully cultured from a man’s semen longer than 24 days after developing symptoms, but Zika ribonucleic acid (RNA) has been found in semen up to 188 days—or just over six months—after symptom onset. According to the WHO, a total eight studies have now examined the presence of Zika in semen.
Whether or not the CDC revises its travel guidance to match the new WHO guidelines remains to be seen.
At present, the CDC still advises women to “wait at least eight weeks [after traveling to an area with active transmission] before trying for a pregnancy.” But CDC spokesperson Tom Skinner told CNN on Tuesday that the agency is “in the process of updating its interim guidance related to pregnancy planning and the timing of pregnancy after possible exposure to Zika virus and prevention of sexual transmission of Zika virus.”
The CDC did not immediately respond to The Daily Beast’s request for comment on the disparity between their current guidance and the WHO’s new interim guidelines. When asked why about this disparity, Epstein told The Daily Beast that “WHO and the CDC have different roles.”
“WHO, as the global guardian of public health, issues evidence-based recommendations for countries all over the world so authorities and groups can make informed decisions on health and safety based on their context, which can vary from region to region, among countries, and even within countries,” Epstein said. “CDC advises people in the U.S. on public health measures they should take.”