As Omicron spreads, the C.D.C. seeks to clarify its message on testing and isolation.

Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, on Sunday defended the agency’s recommendations for a shorter isolation for many people who test positive for the coronavirus.Credit…Cheriss May for The New York Times The Centers for Disease Control and Prevention faced fresh blowback on Sunday for its muddled messaging on…