WHO says Zika virus spreads explosively, four million cases forecast

The Zika virus, linked to severe birth defects in thousands of babies in Brazil, is “spreading explosively” and could infect as many as 4 million people in the Americas, the World Health Organization (WHO) said on Thursday.

Director-General Margaret Chan told members of the U.N. health agency’s executive board the spread of the mosquito-borne disease had gone from a mild threat to one of alarming proportions. The WHO would convene an emergency meeting on Monday to help determine its response, she said.

“The level of alarm is extremely high,” Chan told the Geneva gathering.