For Hooman Kamel, an intensivist at a Manhattan hospital, the weekend just before he started seeing COVID-19 patients in his I.C.U. was the darkest time. Kamel is a witty, blunt-talking doctor who grew up in San Jose and came to medicine by way of Harvard, Columbia, and U.C.S.F. In his ordinary professional life, he is a research physician, and spends most of his time studying the causes and treatment of strokes. In early February, when there were still fewer than a hundred confirmed COVID-19 cases in the United States, Kamel watched the spread of the epidemic with interest but no particular urgency. Toward the middle of that month, he told me recently, his sense of personal alarm began to kick in, not because of any change in external circumstances but because his wife was due, in a few weeks, to give birth to their second child. “There’s this sort of heightened anxiety in general when you’re expecting a kid,” he said. “So a lot of my initial interest was as a doctor in general but also personally thinking, Should we be stocking up on Purell, formula, all this stuff?”

In the weeks after the baby, a boy, was born, Kamel’s anxiety ticked up another couple of notches. Kamel, a self-professed Twitter addict, had been following reports from physicians working in and around Seattle, where the outbreak was intensifying. In mid-March, he came across a Twitter thread that supposedly reproduced notes written by a critical-care doctor working on the front lines. The notes were written in an opaque medical shorthand, and they described a hospital that was desperately short of personal protective equipment (P.P.E.) and overrun with critically ill COVID-19 patients, some of whom were in their twenties and had no underlying medical conditions. “As much as you try to be rational and scientific-minded, I think the brain has a funny way of dismissing things that aren’t directly related to you,” Kamel told me. “So, even given the early reports out of China, and then the stuff out of Italy, there’s this element of, like, O.K., it’s gonna be different here, without being able to specify why it was any different.” But the notes from Seattle were a wake-up call. Within a week, he said, “I was just a complete wreck. I was looking at my son, and thinking, like, How is he going to handle life as an orphan?”

On March 21st, in the midst of his gloom, Kamel got an e-mail from someone he knew from his medical residency, a primary-care physician who works on an Indian reservation in Minnesota. The primary-care physician had seen an article in the Times about quarantine parties taking place entirely online, and he invited—begged, really—other members of their residency class to meet up with him in a Zoom video-conference call.

The virtual cocktail party happened that Saturday night, and the conversation turned so quickly to COVID-19 that Kamel’s baby boy barely rated a mention. Instead, the group of friends talked about how best to manage a disease that five months ago had never been seen in a human being. So far, most of the world’s attention has been justifiably dedicated to stopping the transmission of the disease, whether by quarantines and social distancing or vaccines. But the doctors on the call needed answers to a different question: what to do when COVID-19 showed up at their hospital doors. They needed to know whether it was unusual for patients to get better before they got worse, for instance (no, it seems to happen with some frequency), or whether hydroxychloroquine would exacerbate poor cardiac outcomes (possible, but not likely). In ordinary times, these were the kinds of questions that would get sorted out by randomized trials and meta-analyses, but that kind of science took time that they didn’t have.

The lack of P.P.E. was another concern. Many of the doctors on the call had previously practiced abroad, in places like Bolivia, Uganda, and Haiti, and they’d been in situations where it was not a given that they’d be able to protect themselves against whatever contagions they were treating. Nevertheless, the notion that it might be up to them to secure functional P.P.E. for themselves and their colleagues at hospitals in the United States was a shocking novelty. The Minnesota primary-care physician told his friends that he’d scoured the shelves of his local hardware stores for construction-grade N95 masks and was ready to send bundles to anyone who needed them. A cardiologist who also lived in Minnesota said that she’d been writing letters to her governor about the critical need for more P.P.E.

The urgency of the conversation about P.P.E. stemmed in large part from the same fear that Kamel had been experiencing. Although there is much about COVID-19 that is frightening for everyone—the speed of transmission, the scale of the spread, the medical and economic devastation left in its wake—for health-care workers and others on the front lines of the outbreak, there is a special concern. Without adequate P.P.E., they are at serious risk of contracting the disease themselves. And, since many of the doctors on the call were married, with young children, whatever risks they bore themselves would all but certainly be shared with their families.

Kamel’s wife, who was listening in on the call from the other end of the couch, was, he said, “utterly terrified after our conversation.” However, Kamel told me that seeing the faces of his residency friends, with whom he’d shared some of his most difficult days during his training as a physician, was a “huge existential lift.” “It was very reassuring to feel like I wasn’t going into this alone. We’d done something very difficult in the past, and we can deal with this.”

Kamel and other physicians on the front lines of the pandemic are now operating in an atmosphere of pervasive uncertainty. Though more and more is being learned every day, there is still a tremendous amount of information, some of it very basic, that we simply do not yet have about COVID-19. Information about how a disease spreads among populations, how it progresses in the bodies of patients, and how its clinical course might be shortened or ameliorated is usually considered crucial for doctors trying to figure out how best to care for their patients. For COVID-19, however, all of this is still being sorted out.

Compounding these difficulties is a strong sense among many of the physicians I’ve spoken to that the federal government, and particularly the Centers for Disease Control, has not supplied the sort of clinical leadership that the moment demands. To fill that vacuum, doctors have been able to look to high-impact medical journals and academic institutions, such as the University of Washington, in Seattle, and Brigham and Women’s Hospital, in Boston. But, much like Kamel, they’ve also relied on more informal networks to get the information and the support they need.

Prashant Bhave, a cardiologist in North Carolina, told me that on-the-ground reports he’d heard from friends and former colleagues had given him a useful counterbalance to some of what he’d been seeing and hearing elsewhere. “If you’d watched the Coronavirus Task Force, or the news, you might have gotten a sense that there was a mask shortage,” he said. “But you wouldn’t necessarily understand that there were emergency-department residents using the same mask for a week at a time. I got that through other communities of people who are actually doing the work.”