Researchers warn covid-19 could cause debilitating long-term illness in some patientsIn the fall of 2009, one of us, Beth, was hit by an illness she suspects was H1N1 flu, which was circulating then. In 2012, the other, Brian, developed a sudden fever, which his doctors said was also likely of viral origin. Neither of us recovered, and we're both disabled to this day. The long-term illnesses that can follow viral infections can be devastating - and are devastatingly common. In 2015, the nation's top medical advisory body, the Institute of Medicine, estimated that between 800,000 and 2.5 million U.S. residents live with the illness or illnesses awkwardly named myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). An estimated three-quarters of these cases were triggered by viral or bacterial infections. Now, as a new pandemic virus is burning through the world and causing many deaths, researchers are raising alarms that the novel coronavirus and the covid-19 disease it causes will also leave in its wake a potentially large population with post-viral problems that could be lifelong and, in some cases, disabling. At the National Institutes of Health and elsewhere, scientists who have been studying post-viral ME/CFS are seizing the opportunity to focus on covid-19 patients. They want to understand what biological factors separate those who regain their health from those who remain sick. "We want to look at who recovers and who doesn't," said Avindra Nath, the head of clinical neurology at NIH's Clinical Center in Bethesda, Maryland, who is gearing up to study covid-19 patients. "It's quite possible some will never get their health back." In addition to emerging reports of damage to lungs, kidneys and hearts, covid-19 patients are complaining of ongoing crushing fatigue, muscle pain, cognitive problems and other symptoms that anyone with ME/CFS is...