Hannah Davis misses her old self. Like so many people around the world, she has seen her life upended by long COVID, which has made many once-routine activities impossible. The 32-year-old has stopped working at her job in the field of machine learning and generative models. It’s too cognitively taxing; the lights from display monitors are disorienting. Merely standing up from a sitting position causes her heart rate to shoot to 170 beats per minute, the equivalent of doing a good jog.