The World Health Organization declared an international emergency on Monday over the explosive spread of the mosquito-borne Zika virus, which is linked to birth defects in the Americas, saying it is an “extraordinary event.

The U.N. health agency convened an emergency meeting of independent experts in Geneva to assess the outbreak after noting a suspicious link between Zika’s arrival in Brazil last year and a surge in the number of babies born with abnormally small heads.

“After a review of the evidence, the committee advised that the clusters of microcephaly and other neurological complications constitute an extraordinary event and public health threat to other parts of the world,” WHO Director-General Margaret Chan said.

Up to 4 million cases of the virus are projected for next year, but there are no restrictions on travel or trade.

“If they need to travel, they can get advice from their physician and take personal protective measures, like wearing long sleeves and shirts and pants and use mosquito repellent.”

The last international health emergency struck the world in 2014 when the deadly Ebola virus killed more than 11,000 people. A similar declaration was made for polio the year before.

Read more at JET.