@abd It is my belief after 4 years, that it is an autoimmune disease from the COVID-19 virus. There are those of us who did not get vaccinated and had COVID-19 and there are those that had the vaccines and still got Long COVID. There are so many different symptoms. Most mimic other things like POTS, chronic fatigue, tinnitus, brain fog, arthritis, Lupus, Epstein Barr is reactivated in some, joint and muscle pain, GI issues, depression, anxiety, rashes, vision issues, no taste or smell...the list is long. The research is ongoing. If you go to the CDC or NIH website you can read about it. It is considered a disability. The research is saying that the virus inside T-cells, causes our bodies immune system to actually fight itself. Usually people that have long Covid, had COVID-19 and then got sick with LC several months later.