A case definition for long COVID has yet to be adopted but is referred to by the WHO as “usually 3 months from the onset of COVID-19 with symptoms and that last for at least 2 months and cannot be explained by an alternative diagnosis”; the CDC considers persistent symptoms, or the onset of long-term symptoms, =4 weeks after acute COVID-19 infection.
Many studies and systematic reviews refer to COVID-related symptoms that persist or emerge beyond 4 weeks of infection as consisting of two subsequent phases: 1) Ongoing Symptomatic COVID-19 (OSC; signs and symptoms from 4 to 12 weeks from initial infection) and 2) Post-COVID-19 Syndrome (PCS; signs and symptoms beyond 12 weeks) with respect to symptomatology, abnormal functioning, psychological burden, and quality of life.
Post Acute Sequalae of COVID (PASC) is often referred to in studies and systematic reviews and is commonly understood as “the presence of at least 1 abnormality diagnosed by (1) laboratory investigation, (2) radiologic pathology, or (3) clinical signs and symptoms that were present at least 1 month after COVID-19 diagnosis or after discharge from the hospital”. It can be further classified as short-term PASC as 1 month; intermediate-term, 2 to 5 months; and long-term, as 6 or more months after COVID-19 diagnosis or hospital discharge.
In previous reviews, we have referred to “long COVID” synonymously to the above terms (ie. OSC, PCS, PASC) but for clarity, will move toward using these specific terms as they appear in the literature as well as simply using the time frames reported in each study/review. For example, where needed, we have replaced “long COVID” with the more concise “PASC” or “symptoms beyond 4 weeks of infection”.
Recommendations set out in our 2021 report can be relied upon with an important update to follow-up times (previously 2-3 months). Now, a 4-week follow-up is recommended for diagnosing and managing any PASC, especially for patients who suffered severe acute COVID-19 manifestation, where severe typically refers to those requiring medical attention, such as hospitalization for respiratory difficulty, to manage symptoms during the acute phase. In addition, these follow-ups should include mental health assessments in addition to any relevant clinical testing in response to each patient’s specific symptoms.
The clinical care burden of ongoing COVID-19 symptoms (OCS) is significant in the 3 months after infection and can place great demands on primary care services. Both OSC and PCS have consistently been shown to affect a large portion of the population with complex and persistent challenges that will also place strain on healthcare systems. This involves:
o Complications pertaining to multiple care specialties, with 20-75% of individuals reporting at least 1 persistent symptom 12 or more weeks following COVID-19 diagnosis.
o Neuropsychiatric manifestations (or “NeuroCOVID”) such as smell/taste disorder, memory complaints, anxiety, depression, post traumatic stress disorder (PTSD), concentration difficulties, and sleep disturbances are reported in 20-50% of individuals beyond 4 weeks from infection.
Functional disabilities and incapacity to return to work has been reported in 5% to 90% of individuals, where some are unable to reach their pre-COVID employment level at 12 weeks or longer post-infection; this has the potential to impact all sectors, including various levels of healthcare.
A significant number of individuals suffer from severe clinical conditions, such as acute cardiac, lung, and kidney injury.
A key focus will be to support individuals and populations who experience other persistent yet less severe conditions and symptoms such as fatigue, dyspnea, and mental health challenges including depression, anxiety, and sleep disorders.
July 12, 2021
Long COVID-19 is likely to increase demands across the health system, including emergency departments, hospital admissions, primary care visits, specialist appointments, and home care and rehabilitation services.
The clinical care burden of long COVID-19 is the greatest in the first 3 months after infection (revised from ‘testing’ in the previous report) and is likely to place the greatest demand on primary care services.
Patients with severe COVID-19 illness are more likely to place longer-term demands (4-6 months after the infection) on specialist care due to respiratory, circulatory, endocrine, metabolic, psychiatric and unspecified conditions.
Groot, G; Reeder, B; Hammond, B; Badea, A; Howell-Spooner, B; Ellsworth, C. What are long COVID's demands on the healthcare system, and its severity of the illness? 2022 Jun 20, Document no.: EPM210602v002 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2022. 23 p. (CEST rapid review report).
There exists some ambiguity across jurisdictions and thus there is no clear universal case definition of COVID-19 hospitalization.
Public Health Ontario measures hospitalization as “the number of confirmed COVID-19 cases that reported ever being hospitalized during their infection”- i.e., all cases reported as ever being hospitalized during their infection.
The category “incidental COVID-19 hospitalizations” has been proposed. This refers to patients who are primarily admitted for other ailments and test positive as part of routine screening.
Some jurisdictions and health agencies have started differentiating between those who were admitted for COVID-19-related illness and incidental admissions. Ontario and Saskatchewan have begun using this category in their regular reporting of COVID-19 statistics.
New data from Australia, New Zealand, the US, and Canada indicate that 30 to 50 percent of COVID-19 hospitalizations are “incidental COVID-19 hospitalization” – 46% of COVID-19 hospitalizations in Ontario (as of January 11th, 2022) and 40% in Saskatchewan (as of January 26th, 2022)
Some expert opinions caution that such binary categorization may oversimplify clinical reality, and suggests also employing an ‘indeterminate’ category
Asamoah, G; Badea, A; Reeder, B; Groot, G; Muhajarine, N; Howell-Spooner, B; Young, C. What is the (case) definition of hospitalization for COVID-19 in similar jurisdictions? 2022 Feb 10. Document no.: CAC220101 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2022. 9 p. (CEST rapid review report).
· The terms cluster and outbreak both describe the occurrence of new disease cases within a particular location and time period. The number of cases within a cluster are not necessarily greater than what is expected, however in an outbreak the number of cases does exceed the usual norm.
· In an outbreak the cases are confirmed to be epidemiologically linked while in a cluster an epidemiological connection is only suspected.
· Not all clusters are outbreaks, however each cluster needs to be investigated
· Understanding how to characterize COVID-19 cases based on a suspected or proven epidemiological link can better guide prevention of disease spreading
Radu, L; Badea, A; Groot, G; Ellsworth, C; Young, C. What is the definition of an outbreak versus a cluster for COVID-19 in different clinical and community settings in Canada, the US, and the UK? 2020 Jul 27; Document no.: EOC071001 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 11 p. (CEST rapid review report)