Evidence the Zika virus is causing severe birth defects and a paralyzing nerve disease is "alarming", the World Health Organization says, and officials should not wait for absolute proof to take action.
There's also evidence that sexual transmission of the virus is more common than anyone thought, WHO's director-general Dr. Margaret Chan said. That gives the virus a chance to infect people in places far from the mosquitoes that usually spread it.
WHO has been cautious in warning the world about Zika, even as national agencies such as the U.S. Centers for Disease Control and Prevention have been quick to advise pregnant women to stay away from affected countries and to ask men to wear condoms when they come back from Zika zones.
Chan said the evidenced is becoming ever stronger that Zika causes a range of severe birth defects, including microcephaly, and Guillain-Barre syndrome, a paralyzing reaction to infections and, sometimes, to vaccines.
"All of this news is alarming," she told a meeting of WHO's emergency committee.
"Concerning the link with fetal malformations, the virus has been detected in amniotic fluid. Evidence shows it can cross the placental barrier and infect the fetus. We can now conclude that Zika virus is neurotropic, preferentially affecting tissues in the brain and brain stem of the developing fetus," Chan said.
"Nine countries are now reporting an increased incidence of Guillain-Barré syndrome or laboratory confirmation of a Zika virus infection among GBS cases. intensive care unit for as long as 51 days," she added.
"Growing evidence of a link with GBS expands the group at risk of complications well beyond women of child-bearing age. GBS has been detected in children and adolescents but is more common in older adults and slightly more common in men. The anticipated need for expanded intensive care adds a further burden on health systems," Chan said.
"Reports and investigations from several countries strongly suggest that sexual transmission of the virus is more common than previously assumed."
So WHO strengthened its recommendations on travel, telling pregnant women straight up to stay away from Zika-affected countries.
WHO strengthened travel recommendations, advising pregnant women not to travel to locations experiencing an outbreak of the virus. Before, it had advised women to consider delaying travel to these areas.
"What we see in Brazil now is what could occur in Colombia and other countries in coming months," said Dr. David Heymann, an infectious disease specialist who chairs WHO's emergency committee.
"We felt we needed to make this recommendation," he added.