U.S. public health officials have been told to stop working with the World Health Organization, effective immediately. A U.S. Centers for Disease Control and Prevention official, John Nkengasong, sent a memo to senior leaders at the agency on Sunday night telling them that all agency staff who work with the WHO must immediately stop their collaborations and “await further guidance.” The Associated Press viewed a copy of Nkengasong's memo, which said the stop-work policy applied to “all CDC staff engaging with WHO through technical working groups, coordinating centers, advisory boards, cooperative agreements or other means — in person or virtual.”