Published 24 January 2021 The term “Long COVID-19” covers a wide spectrum of symptoms that can occur or persist weeks and even months after an acute infection, not only after severe but also after initially mild courses. Primary symptoms are exhaustion and fatigue, but also dyspnea on exertion, headache and arthralgia, palpitations, concentration disorders and depressive symptoms in previously healthy individuals. The symptoms may fluctuate within hours or days. This chapter summarizes current knowledge (which is still limited, as of the end of January 2021).