Long COVID is an overarching term that was originally coined by patients and is widely used to describe ongoing symptoms after the acute phase of COVID-19, including both short-term symptoms (4–12 weeks) and longer-term sequelae (beyond 12 weeks). The term post-COVID-19 condition, developed by WHO, describes the continuation or development of new symptoms 3 months after the initial SARS-CoV-2 infection.The incidence of long COVID is estimated to be 10–30% for people who are not hospitalised in the acute phase, 50–70% for hospitalised patients, and 10–12% for vaccinated individuals after acute infection. Conservatively, at least 65 million individuals globally were estimated to have long COVID in 2023, with cases increasing daily.
Long COVID is a complex, multisystem condition with the potential to have a substantial impact on individuals and society, including increased disability, increased health-care costs, and economic and productivity losses. More than 200 symptoms have been identified that can impact functioning and activities of daily living, encompassing physical, psychological, and cognitive function. The symptoms and sequelae of long COVID can persist for weeks or months, fluctuate over time, or manifest as new-onset chronic conditions. The condition has placed an enormous burden on health-care systems. Despite some international collaboration, progress in understanding long COVID has been hindered by heterogeneous study designs, follow-up durations, and measurement methods. A global, collaborative, multidisciplinary research agenda will be essential to improve the diagnosis and treatment of long COVID.