An estimated 65 million people worldwide suffer from prolonged COVID. The disease can damage the brain, heart, blood vessels and immune system for a long time even after the acute infection has been overcome. Scientists associate the symptoms of long-term COVID with the persistence of the virus in the body, with inflammation, with microclots in blood vessels and with disturbed energy metabolism of cells. Structured rehabilitation and various stimulation methods can improve patients' quality of life. Experimental treatments, such as antivirals, metformin, therapies targeting the gut microbiome, and biologics are also being investigated. However, the evidence so far is limited, as large and unequivocal clinical studies are still lacking.