President Donald Trump used one of the flurry of executive actions that he issued on his first day back in the White House to begin the process of withdrawing the U.S. from the World Health Organization for the second time in less than five years — a move many scientists fear could roll back decadeslong gains made in fighting

President Donald Trump is pulling the U.S. out of the World Health Organization, raising concerns about the U.N. agency's ability to fight diseases and respond to emergencies around the globe without its biggest funder.