In December of 2012, I came down with what at first looked like a bad case of mononucleosis. I felt tired and had a sore throat, a cough, and a slight fever. At the time, I was twenty-six and working as an adjunct English professor at a small college in Westchester, New York. It was Christmas break, so I thought that I would sleep it off and feel better by the New Year. But over the next few months my symptoms grew to include muscle pain, migraines, and occasional vertigo. The cough went away but the tiredness got worse, and by the summer I was spending half my time resting in bed. I was used to playing pickup basketball several times a week after work, but now a few pushups left me exhausted. I couldn’t figure out what was happening. One afternoon, as an experiment, I went for a run near my apartment, in uptown Hoboken. I clipped my iPod Shuffle to my mesh shorts and jogged past Italian delis with dry-cured sausages in their windows and along a pier that hugged the Hudson. It felt amazing. But the next day, while grading papers with a few other teachers, suddenly, I became dizzy and weak. I left the office without explanation, and, for the next several days, I barely left my bedroom.

After a year of these symptoms, I visited an internist in Manhattan, who gave me a diagnosis: I had chronic-fatigue syndrome. According to the National Academies of Sciences, C.F.S. (sometimes referred to as myalgic encephalomyelitis) affects between eight hundred thousand and two and a half million Americans and is characterized by extreme exhaustion. Patients with severe cases are bedridden for years and rarely move or speak. Doctors are still not sure what causes it. For decades, many thought that it was psychosomatic. (My symptoms were so odd that, over the preceding year, I, too, had wondered if I was going crazy.) This sense lingers in popular culture. In the pilot episode of “House,” from 2004, a patient comes to the clinic complaining of C.F.S., and Dr. House successfully treats him with mints from the vending machine. In a standup set in 2007, Ricky Gervais joked about people who say they have C.F.S. because they “don’t feel like going to work.” Today, though, most doctors who study C.F.S. think that its symptoms are caused by a dysfunction of the immune system, which is typically triggered by an infection, such as the Epstein-Barr virus (which causes mono) or viral encephalitis. Still, they don’t understand why, even as most people bounce back from these ailments, a small percentage of them never recover. Because there’s no clear biological cause, doctors recognize the disease by gauging symptoms subjectively, which makes diagnosis, in the eyes of skeptics, unreliable, and has kept away funding for research. There are currently no F.D.A.-approved medications to treat C.F.S.

Over the following three years, I saw a dozen doctors, who prescribed a range of treatments. The internist in Manhattan put me on injections of an amino acid derived from the livers of Argentine cows. On a few occasions, leaving his office, I experienced an energizing high that was either a temporary response to the cow liver or a marvellous placebo effect; it always wore off within a day, and I was later taken off the drug. An endocrinologist gave me a medication that stimulated my thyroid. Some patients resort to folk remedies, like kombucha tea or licorice, or riskier treatments, such as amphetamines or shots of hydrogen peroxide. I tried testosterone creams, antiviral pills, blood-plasma infusions, and so, so many nutritional supplements. Nothing stuck, except the medical bills, and I was running out of specialists in the area who could help.

In 2016, I heard about an internist named Daniel Peterson, who was treating patients in Incline Village, Nevada, with an experimental medication called Ampligen. Few outside the isolated network of C.F.S. patients, caregivers, and specialists have heard of Ampligen, but, within the illness’s sphere, the drug has developed a fabled reputation. In 2012, the F.D.A. provisionally rejected Ampligen’s application for approval, because trial results had not conclusively proved that it was effective; Peterson is gathering more evidence to re-apply. Because data is limited, the drug’s reputation hinges on anecdotal evidence, which should, of course, be considered with caution. But C.F.S. patients are very active in online message boards, and, when I Googled Ampligen, I came across powerful stories about the drug’s effects. In a patient testimony from 1998 that was posted online, a woman named Karen, who was functionally disabled by C.F.S., wrote that, after three months on Ampligen, she was well enough to do her taxes again and go skiing with her son. A blogger named Kelvin wrote on a Web site called The New Ampligen Diaries that, after getting on the drug, he “started to experience a taste of ‘normal’ life—a free life—for the first time in a very long time!” The Web site for the American Myalgic Encephalomyelitis and Chronic Fatigue Syndrome Society quoted Kenny De Meirleir, a doctor based in Belgium, as saying that eighty per cent of his patients reported “complete clinical recovery” on Ampligen. (De Meirleir later told me that, in fact, only a small subset of his patients had fully recovered.)

Peterson first discovered Ampligen’s potential for treating C.F.S. in the late nineteen-eighties, and, since then, patients have moved to Incline Village from all over the country to get on the drug. Ampligen is administered as a twice-weekly infusion, and it suppresses symptoms but doesn’t cure them, meaning that treatment needs to be continuous in order to remain effective. Some patients have stayed in Incline for only a few months of temporary treatment, but many have settled there permanently, hoping to take the drug for the rest of their lives. In all, Peterson treats some fifty C.F.S. patients who live in the area full time, and periodically sees around eight hundred more. I had no idea whether it would work for me, but I had little to lose. In the summer of 2016, I quit my job, packed up whatever would fit in my car, and drove across the country in the hopes of getting on Ampligen.

Incline Village is an affluent town of nine thousand people, perched on the north shore of Lake Tahoe and shrouded in ponderosa pines. Its stunning natural beauty and proximity to beaches and ski slopes have made it a vacationers’ paradise. Peterson’s treatment center, Sierra Internal Medicine, is situated in a brown-stucco building near one of the lake’s bays. Inside, patients sit for doses of Ampligen in the infusion room, largely in silence, while nurses tend to their I.V. bags and researchers pore over blue binders. Peterson, who is sixty-eight, with broad shoulders and a mustache, shuffles through the office quietly. He has become a kind of folk hero among his patients. Anita Patton, a fifty-seven-year-old mother of three who recovered from C.F.S. on Ampligen, told me that Peterson “was directly responsible for giving me the health to raise my children.” Anthony Komaroff, an internist at Harvard who studies C.F.S., said that Peterson had doggedly researched the disease for decades, “against a lot of negative feelings among some of his colleagues.” On the wall of the infusion room at Sierra Internal hangs a cartoon of Peterson and his former partner, Paul Cheney, amid a clutter of beakers and textbooks, captioned “Cheney & Peterson Turned into the Woodward & Bernstein of Clinical Medicine!”