UN health chief: Zika virus is ‘spreading explosively’

The Zika virus is “spreading explosively” in the Americas, which could see up to 4 million cases over the next year, international health officials said Thursday, announcing a special meeting next week to decide if they should declare an international health emergency. The warning from the World Health Organization came amid a call to arms by officials on both sides of the Atlantic over the mosquito-borne virus, which has been linked to a spike in a rare birth defect in Brazil. Brazil’s president — noting there is no medical defense against the infection — called for a crusade against the mosquitoes spreading it. “As long as we don’t have a vaccine against Zika virus, the war must be focused on exterminating the mosquito’s breeding areas,” said President Dilma Rousseff. The U.N. health agency called the special session in part to convey its concern about an illness that has sown fear among many would-be mothers....