It said sexual transmission was “relatively common” and that health services in Zika-affected areas should be ready for potential increases in cases of neurological syndromes such as microcephaly and congenital malformations.
“Pregnant women whose sexual partners live in or travel to areas with Zika virus outbreaks should ensure safe sexual practices or abstain from sex for the duration of their pregnancy,” the WHO said in a statement, based on advice from its Emergency Committee of independent experts.
Previously the UN health agency had advised women to consider deferring non-essential travel to areas with ongoing transmission of the mosquito-borne virus, which is spreading through Latin America, including Olympics host Brazil.
The link between Zika and babies born with small heads and developmental problems, as well as Guillain-Barre syndrome which can cause paralysis, has not been proven scientifically but studies point in that direction, it said.
“Clearly Zika infection during pregnancy will produce very bad outcomes,” WHO director-general Margaret Chan told a news conference. “It is important we recommend strong public health measures and not wait until we have definitive proof.”
David Heymann, who chairs the WHO Emergency Committee set up on February 1, said of the recommendation: “The onus is on countries to identify and report where they have outbreaks and where they don’t.”
The WHO did not recommend any general trade or travel restrictions. But it said that existing mechanisms under the WHO’s International Health Regulations should be explored, including recommendations that airports be sprayed to eliminate mosquitoes and their breeding grounds.
“We can expect more cases and further geographical spread,” Chan said. “Sexual transmission is more common than previously assumed.”
Bruce Aylward, WHO Executive Director for Outbreaks and Emergencies, told reporters that sexual transmission had only been documented as spreading from men to women.
“There’s no evidence of women-to-men (transmission), so this dead-ends,” he said.