Jan 28, 2016 3:32 PM by NBC News
Experts strongly suspect that Zika is causing a severe birth defect called microcephaly, in which babies' brains are underdeveloped. It's not certain yet, but evidence is building.
'The possible links, only recently suspected, have rapidly changed the risk profile of Zika, from a mild threat to one of alarming proportions," Chan said in remarks to WHO's executive board.
"The increased incidence of microcephaly is particularly alarming, as it places a heart-breaking burden on families and communities." But WHO officials stressed there were still doubts about what might actually be causing the rise in microcephaly in Brazil and note a similar increase in cases has not been seen in other countries that have or have had Zika.
At least 23 countries have local spread of Zika and WHO says the virus will likely eventually spread to almost every country in the Americas except Canada and Chile, which don't have the mosquito species that transmits the virus.
WHO's assistant director general, Dr. Bruce Aylward, said the spread of the virus has not reached the highest level of alert for the organization. "Alarmed would not be the right language," Aylward told reporters."I think concerned would be the right language to use."
The main goal is to get out some coherent travel advice for people, Aylward said. He said it would be very unlikely that WHO would recommend against all travel to Brazil. Such a recommendation would be devastating to Brazil's economy.
WHO can also set a research agenda and help direct any needed aid efforts. Aylward said this will be the first big test of a new central emergency response mechanism set up after WHO admitted it had failed to respond quickly enough to the Ebola epidemic in West Africa.
On Wednesday, two experts on international health matters accused Chan and WHO of acting far too slowly in raising the alarm about Zika. They welcomed WHO's decision.
"The Director-General has taken a critical first step in recognizing the seriousness of an emerging epidemic," said Dr. Lawrence Gostin, who heads the O'Neill Institute for National and Global Health Law at Georgetown University.
"She now must urgently mobilize international resources to curb the rapid spread of Zika worldwide, including aggressive mosquito control, active surveillance, accelerated vaccine research and travel advisories for pregnant women. It is far better to be over-prepared than to wait until a Zika epidemic spins out of control."
Until last year, the virus had not been a major concern for health officials, causing mostly mild symptoms in around 20 percent of those infected.
"The situation today is dramatically different," Chan said. "The level of concern is high, as is the level of uncertainty... Questions abound. We need to get some answers quickly."
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