BALDWIN PARK, Calif.—On New Year’s Day at Kaiser Permanente’s medical center in this suburb east of Los Angeles, the overflowing emergency room spilled into the hallway. Doctors treated patients on oxygen in the waiting room after running out of beds. Some 80% of patients admitted in recent days have Covid-19.

In Texas, patients who need to be transferred from small facilities to big metropolitan hospitals sit in limbo for hours or days, putting them at risk of developing complications from delays. Desperate smaller hospitals have flown patients as far as Albuquerque, N.M., and Oklahoma City for an open bed.

In North Carolina, rising numbers of intensive-care patients in Charlotte have forced doctors to save those beds for the “sickest of the sickest” from Covid and find somewhere else in hospitals for all other critically ill patients, one hospital official said.

Across the nation, the surge of coronavirus cases is crowding large metro hospitals with Covid-19 patients, pushing occupancy against the limits of space and overwhelming nurses and doctors. More than 40% to 60% of ICU patients in some metro areas are critically ill from Covid-19, according to an analysis of federal data by the University of Minnesota Hospitalization Tracking Project.