The World Health Organisation has declared a “public health emergency of international concern” due to the apparent link of the Zika virus to a surge in serious birth defects in South America.

WHO chief Margaret Chan said the link between the Zika virus and microcephaly was “strongly suspected but not yet scientifically proven.”

“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,” Chan said.