One morning in March, 2020, Diana Berrent, a photographer and a mother of two from Long Island, woke up with a fever. She had chills, diarrhea, and a heaviness in her chest, and grew concerned. Her daughter was hosting a sleepover; Berrent made her way to the basement and asked the other girls to leave. Then she went into isolation for eighteen days.

Berrent had followed the news of the coronavirus from Wuhan to Lombardy and Tehran. But, she told me recently, “in suburbia, no one expects to be the first person on their block to get the plague.” She tried to get tested, but testing was limited mostly to people who’d been hospitalized. She eventually received a covid-19 diagnosis, after an acquaintance connected her to a local congressman who arranged a test. On Facebook, she conducted her own contact tracing. A few days before falling ill, she had photographed an event in a crowded elementary-school gymnasium, and she was convinced that she was Patient Zero. At the time, there were scattered reports of coronavirus cases, but few people admitted to being infected, and her social-media updates went viral. The New York Post gave Berrent a daily column in which to chronicle her illness. She started a video blog detailing her symptoms, isolation, and recovery. In one HGTV-inspired episode, she instructed viewers on “how to set up your perfect isolation room.”

Berrent started a Facebook group called Survivor Corps, as a sort of “Tinder for plasma,” she said. Within a week, the group had more than ten thousand followers. On its page, Berrent wrote that people infected by the coronavirus were “waiting to be superheroes.” Later, when monoclonal antibodies were shown to be effective at fighting covid-19, she began working with the pharmaceutical company Regeneron and the health-care firm Optum to help people arrange home delivery of the treatment.

Survivor Corps now has more than a hundred and seventy-five thousand members—it is the largest grassroots covid movement in the world. These days, Berrent meets regularly with government officials, leading scientists, patient-advocacy groups, and covid survivors and their families. Not long ago, she gave presentations to the Centers for Disease Control and Prevention, the National Institutes of Health, and a White House coronavirus task force within the same week. She appears on podcasts and panels, and sits on a number of covid committees at universities and within government, sometimes as the only patient advocate. “I’m now being asked to peer-review medical papers, and I haven’t taken biology since tenth grade,” she said.

Survivor Corps has no physical headquarters. It is, in essence, a huge Facebook group with an associated Web site. People share stories of lost parents and children; they ask for prayers and support; they vent about an unfeeling health-care system. They describe debilitating symptoms that they attribute to long covid: problems with their livers, legs, lungs, stomachs, skin, teeth, memories, and moods. They speculate about biological theories and swap medical advice, some of it valid, but some unsupported or proved ineffective. (The group, which is lightly moderated, has rules against “unsubstantiated” medical advice and conspiracy theories.) Occasionally, someone voices skepticism about what people are posting. “I am astonished at what a very close friend just said to me,” one member posted. The friend had accused her of reading “what a bunch of people write” but having “no idea if they’re telling the truth. They just tell you what you want to hear so you can blame all your issues on being sick 9 months ago.”

Advocating for such a vast constituency has pulled Berrent into choppy scientific waters. Historically, patient advocates have often found themselves opposing the researchers with whom they are trying to partner; aids activists frequently clashed with scientists, demanding faster research and more treatments, and in May, 1990, hundreds of act up members protested outside the National Institute of Allergy and Infectious Diseases, which Anthony Fauci had been leading for half a decade. More recently, advocates have worked on behalf of people who say they suffer from chronic-fatigue syndrome, fibromyalgia, chronic Lyme disease, and other conditions that some researchers consider ill-defined.

There is little doubt among researchers that long covid exists. But the syndrome is new, and lives for the moment in the realm of theory and anecdote….