Lynne Hewett, a Utah nurse, flew into New York City a couple of weeks ago, to work the front lines of the coronavirus pandemic. She was an emergency room nurse in New York, after 9/11 and Superstorm Sandy. She was in Haiti after the earthquake.

Now, she’s in a Manhattan hospital’s emergency room, treating an onslaught of New Yorkers who have coronavirus, or worry that they do. She’s never seen anything like it.

“It’s overwhelming,” Ms. Hewett said. “These are really, really sick patients coming in, needing 10 or 11 people to work on them. These patients are coding” — or going into cardiac arrest. “There’s not enough staff to have a break and regroup; it’s nonstop. You’re trying to do one person, then you turn around and hear, ‘You’ve got another code next door.’”

For many medical providers, such stress is the new norm. They’re coping with, or prepping for, crowds of sick or anxious patients and inadequate stores of personal protective equipment (P.P.E.). On the job, they expose themselves and by proxy their families, to a frightening disease. They’ve watched colleagues sicken or die from it.