“Every single phase of life has been selected to try to avoid parasitism,” Stephen Hedrick, an immunologist at the University of California, San Diego, told me. “Bacterial or viral populations are truly vast in size,” Robert Jack and Louis Du Pasquier write, in “Evolutionary Concepts in Immunology,” and the wide variation among them gives natural selection many candidate organisms upon which to work. Our circulatory system doubles as a communications network; our blood vessels have an “endothelial” lining—a surface that is charged with the intelligent routing of immune cells. In response, the blood vessels swell, creating off-ramps through which white blood cells, which are part of the immune system’s circulating defense force, can flow toward the site of infection. Contemplating the enormous amounts of information that it collects and synthesizes throughout the body, Jack and Du Pasquier suggest that “the immune system can be regarded, above all else, as a computational device.” Our guts burble with foreign microbes outnumbering human cells roughly ten to one, but the good are seamlessly sorted from the bad; every day, some of our cells grow into cancers, but the immune system dispatches them before they become dangerous. But, as the coronavirus pandemic began to escalate in the U.S., they initiated a side project, infecting lung cells in a dish with SARS-CoV-2, the virus that causes COVID-19, and studying the results. They would take half a dozen viruses—including SARS, MERS, and the new coronavirus—and induce infections in hosts, starting with cells in a petri dish and graduating to ferrets. The infections took place inside the lab’s Biosafety Level-3 facility, a series of nested rooms in which each is kept at a lower pressure than the one surrounding it, so that air flows inward and up an exhaust chute containing sensitive filters. In the “warm zone,” where there is always the danger of being exposed to a live virus, you must wear a gown, two sets of gloves, two sets of shoe covers, a respirator mask, a face shield, and a bouffant cap. The process takes sixteen hours to complete, and Møller, who during the height of the pandemic lived in Greenpoint, Brooklyn, often biked home at dawn over the Pulaski Bridge.