Most people with COVID-19 got sick, recovered, and moved on. A subset did not. Months in — sometimes over a year — they are still exhausted after climbing a flight of stairs, still losing words mid-sentence, still waking up as tired as when they went to bed. This is Long COVID, and by some estimates it now affects somewhere between 10 and 30% of those who contracted the virus. The numbers are staggering. The biology behind it is stranger than most people expect. Here is what makes Long COVID different from typical post-viral fatigue: the immune response does not resolve. It just keeps going.