KIRKLAND, Wash. — The hardest day of Debbie de los Angeles’s life had been the day she put her mother into a nursing home. That was before coronavirus.

As fatal infections spread through the Life Care Center in suburban Seattle, where her 85-year-old mother lived, Ms. de los Angeles had tried not to worry. Nurses were monitoring her mother’s temperature. They reassured Ms. de los Angeles that her mother had no fever, cough or other signs of infection.

But at 4:15 a.m. on Tuesday, a nurse called with troubling news. Her mother, Twilla Morin, had developed a 104-degree fever. They were giving her Tylenol. Then the nurse confirmed her do-not-resuscitate orders.

“We anticipate that she, too, has the coronavirus,” a voicemail message from a nurse said. “We do not anticipate her fighting this.”