The World Health Organization on Friday announced that the Zika virus outbreak, linked to deformations in babies' heads and brains, no longer poses a world public health emergency, though it warned the epidemic remains a challenge. Brazil, the epicentre of the outbreak, has however refused to downgrade the risk, while experts swiftly lashed out against the world health body's decision. “The Zika virus remains a highly significant and long term problem, but it is not any more a public health emergency of international concern,” the world health body's emergency committee chair Dr David Heymann said.