text:  Post COVID 19 syndrome epidemiology diagnostic criteria and pathogenic mechanisms involved Many patients with mild or severe COVID 19 do not make a full recovery and have a wide range of chronic symptoms for weeks or months after infection often of a neurological cognitive or psychiatric nature The epidemiological evidence diagnostic criteria and pathogenesis of post COVID 19 syndrome are reviewed Post COVID 19 syndrome is defined by persistent clinical signs and symptoms that appear while or after suffering COVID 19 persist for more than 12 weeks and cannot be explained by an alternative diagnosis The symptoms can fluctuate or cause relapses It is a heterogeneous condition that includes post viral chronic fatigue syndrome sequelae in multiple organs and the effects of severe hospitalisation post intensive care syndrome It has been reported in patients with mild or severe COVID 19 and irrespective of the severity of the symptoms in the acute phase Between 10 and 65 of survivors who had mild moderate COVID 19 present symptoms of post COVID 19 syndrome for 12 weeks or more At six months subjects report an average of 14 persistent symptoms The most common symptoms are fatigue dyspnoea anxiety depression and impaired attention concentration memory and sleep The underlying biological mechanisms are unknown although an abnormal or excessive autoimmune and inflammatory response may play an important role Clinical manifestations are diverse fluctuating and variable although fatigue and neurocognitive complaints predominate There is no defined consensus on post COVID 19 syndrome and its diagnostic criteria have not been subjected to adequate psychometric evaluation 