Long COVID Diagnosis and Characteristics

Definition and Diagnostic Criteria

The World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) define Long COVID as symptoms persisting beyond 12 weeks from acute COVID-19 diagnosis that cannot be explained by another condition, with the WHO and CDC providing similar definitions 1, 2, 3
Long COVID can be classified as Definite, Probable, or Possible, based on laboratory confirmation and epidemiological link 1, 2
The syndrome can also be described as post-acute COVID, which includes symptoms persisting from 4 to 12 weeks after confirmed acute infection, with specific complications like thyroiditis, myocarditis, and venous thromboembolism 1, 2

Primary symptoms of Long COVID include fatigue (31-58%), dyspnea/shortness of breath (24-40%), cognitive impairment or "brain fog" (12-35%), sleep disturbances (11-44%), musculoskeletal pain (9-19%), cough (7-29%), anosmia/dysgeusia (10-22%), and chest pain (6-17%) 1, 2, 3, 4, 5, 8, 9, 10, 11
The most prevalent symptom is fatigue, affecting 31-58% of patients 1, 2, 3

Long COVID substantially impairs quality of life, with 57% of patients reporting decreased quality of life beyond 12 weeks, and 12.5% unable to envision coping with their symptoms long-term 1, 8
The syndrome considerably affects patients' ability to return to daily activities and work 1, 8

The mechanisms driving Long COVID involve multiple interconnected pathways, including viral persistence, immune dysregulation, autoimmunity, neuroinflammation, endothelial dysfunction, and metabolic disturbances 1, 7
Activation of the kynurenine pathway is associated with cognitive and sleep disturbances 7

The two most consistent risk factors for developing Long COVID are acute COVID-19 severity and female sex, with women having an estimated two-fold increased risk of developing Long COVID symptoms 1, 2, 12

Long COVID is a diagnosis of exclusion, and serious or life-threatening conditions must be ruled out before considering Long COVID 12
Any patient with persisting or new symptoms lasting more than 12 weeks after acute COVID-19 should be referred to medical care 12