On his first day in office, President Donald Trump signed an executive order withdrawing the U.S. from the World Health Organization (WHO)—a move that experts say makes the U.S. and other countries less safe from infectious diseases and other public-health threats. 

“For Americans it may not be obvious immediately what the impact will be, but given the world we live in and all of the factors that are driving more disease outbreaks, America cannot fight them alone,” says Dr. Ashish Jha, dean of the school of public health at Brown University and former White House COVID-19 Response Coordinator. “We need an effective WHO to not just keep the world safe from these diseases, but to keep Americans safe from these diseases.”