The advice targets people in 46 countries throughout Central America, South America, and the Caribbean who may be considering having a baby in the near future. The virus, which is carried by mosquitoes and can be transmitted sexually, does not typically harm infected adults who only carry the virus temporarily, although in rare cases it has provoked paralysis and death.

The most pressing issue the disease presents is the severe birth defects that it inflicts on the infants of infected women. Babies born with Zika often suffer from incomplete brain development and have abnormally small heads, a condition referred to as microcephaly.

Although there have been cases of Zika in the United States, so far they have all involved people who have traveled from countries south of the border. So far three babies born in the U.S. have had birth defects tied to the disease.

The vast majority of Zika-afflicted babies have been born in Brazil, where the tally now stands at over 1,500.

Ever since the disease began to emerge late last year, the WHO has sought to walk a fine line between encouraging necessary prevention efforts and not creating panic. However, deciding where to place that line has been a challenge, especially since understanding of the disease has continued to evolve over the past six months.

Two weeks ago, for instance, the Centers for Disease Control in Atlanta suddenly changed its recommendation on how long people who have recently traveled to Latin America should wait before engaging in unprotected sex. The original recommendation of four weeks was bumped up to eight.