A common approach to viral infections follows the aphorism “What doesn't kill you makes you stronger.” This is only somewhat accurate. In plenty of cases, if you get sick and then recover, your body goes back to its usual functions with the added bonus of natural immunity. But experts and patients have known for a while that some viruses, bacteria, and parasites take a heavier toll: Damage to organs and tissues leaves the body weaker long after the microbial invader is gone, creating chronic conditions.



Now, two years into a devastating pandemic, COVID-19 is bringing this message home in a big way.



Estimates for the number of people who develop long COVID—a suite of lingering symptoms—range from 10 percent