NEW YORK U.S. public health officials have been told to stop working with the World Health Organization ( WHO ), effective immediately. A U.S. Centers for Disease Control and Prevention ( CDC ) official, John Nkengasong, sent a memo to senior leaders at the agency on Jan. 26 night telling them that all staff who work with the WHO must immediately stop their collaborations and “await further guidance.” Experts said the sudden stoppage was a surprise and would set back work on investigating and