Long COVID refers to symptoms that persist or emerge after the acute phase of SARS CoV 2 infection, usually beyond 4 to 12 weeks. It can follow mild, moderate or severe initial illness and affects adults, children and adolescents. Prevalence estimates vary, but a substantial minority of infected people report ongoing problems.

Symptoms cluster into several domains. Common physical symptoms include fatigue, shortness of breath, chest pain, palpitations, cough, muscle and joint pain, headaches and altered smell or taste. Cognitive and neurological issues such as “brain fog,” memory and concentration problems, sleep disturbance, dizziness and neuropathic pain are frequent. Many patients also experience anxiety, depression and post traumatic stress symptoms. Symptoms often fluctuate over time, sometimes triggered by exertion or stress.

Proposed mechanisms include persistent viral reservoirs, immune dysregulation, autoimmunity, endothelial dysfunction, microclots, dysautonomia and mitochondrial impairment. No single mechanism explains all cases, suggesting multiple overlapping pathways.

Diagnosis is clinical and based on symptoms following a confirmed or probable infection, after excluding alternative explanations. There is no specific diagnostic test. Risk factors include female sex, middle age, higher BMI, comorbidities and more severe acute disease, though long COVID can occur after mild infections.

Management focuses on symptom control, rehabilitation and pacing of physical and cognitive activity to avoid post exertional symptom exacerbation. Multidisciplinary care is often needed. Some medications target specific symptoms, for example for autonomic dysfunction, pain or sleep issues. Vaccination reduces but does not eliminate the risk of long COVID. Research is ongoing into biomarkers, targeted therapies and long term outcomes.