Long COVID, also known as Post-Covid-19 syndrome, post-acute sequelae of COVID-19 (PASC), or chronic COVID syndrome (CCS), is a condition characterized by long-term sequelae appearing or persisting after the typical convalescence period of COVID-19. Long COVID can affect nearly every organ system with sequelae including respiratory system disorders, nervous system and neurocognitive disorders, mental health disorders, metabolic disorders, cardiovascular disorders, gastrointestinal disorders, malaise, fatigue, musculoskeletal pain, and anemia.[4] A wide range of symptoms are commonly discussed, including fatigue, headaches, shortness of breath, anosmia (loss of smell), parosmia (distorted smell), muscle weakness, low fever and cognitive dysfunction.

The exact nature of symptoms and number of people who experience long-term symptoms is unknown and varies according to the definition used, the population being studied, and the time period used in the study. A survey by the UK Office for National Statistics estimated that about 14% of people who tested positive for SARS-CoV-2 experienced one or more symptoms for longer than 3 months.[6] A study from University of Oxford of 273,618 survivors of COVID-19, mainly from the United States, showed that about 37% experienced one or more symptoms between 3 to 6 months after diagnosis.

While studies into various aspects of long COVID are under way, as of November 2021, the definition of the illness is still unclear, as is its mechanism. Health systems in some countries and jurisdictions have been mobilized to deal with this group of patients by creating specialized clinics and providing advice.[10][11][12] Overall, however, it is considered by default to be a diagnosis of exclusion.

Source: https://en.wikipedia.org/wiki/Long_COVID