1.1 Case definition

Use the following clinical case definitions to identify and diagnose the long-term effects of COVID-19:

  • Acute COVID-19
    • Signs and symptoms of COVID‑19 for up to 4 weeks.
  • Ongoing symptomatic COVID-19
    • Signs and symptoms of COVID‑19 from 4 weeks up to 12 weeks.
  • Post-COVID-19 syndrome
    • Signs and symptoms that develop during or after an infection consistent with COVID‑19, continue for more than 12 weeks and are not explained by an alternative diagnosis.
    • It usually presents with clusters of symptoms, often overlapping, which can fluctuate and change over time and can affect any system in the body. Post‑COVID‑19 syndrome may be considered before 12 weeks while the possibility of an alternative underlying disease is also being assessed.

In addition to the clinical case definitions, the term ‘long COVID’ is commonly used to describe signs and symptoms that continue or develop after acute COVID‑19. It includes both ongoing symptomatic COVID‑19 (from 4 to 12 weeks) and post‑COVID‑19 syndrome (12 weeks or more).

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