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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes coronavirus disease (COVID-19) . The effects of COVID-19 have been characterised across different time points:
- Acute COVID-19 infection with signs and symptoms of COVID-19 for up to 4 weeks.
- Ongoing symptomatic COVID-19 with signs and symptoms of COVID-19 from 4 weeks up to 12 weeks.
- Long term consequences of COVID-19 which usually presents with clusters of symptoms, often overlapping, which can fluctuate and change over time and can affect any system in the body for more than 12 weeks.
The long term sequelae of COVID-19 awaits consensus definition, and a variety of nomenclature has been used to describe the long term signs and symptoms of COVID-19. This includes the patient directed terms "Long Covid" , "Long-Haul Covid"  and "Long Haulers" , plus other terms including "Post-COVID-19 syndrome" , "Post-COVID Syndrome" , "Post-Acute COVID-19" , and "Post-Acute COVID-19 syndrome". For the purposes of consistency, this page will refer to the long term consequences of COVID-19 as "Long Covid" and to "People living with COVID-19". We will refer to "Long Covid" because this term acknowledges that disease cause and course are as yet unknown, makes clear that “mild” COVID-19 is not necessarily mild, avoids “chronic,” “post” and “syndrome” that may delegitimise peoples experiences, draws attention to morbidity, and centres people with disability . We will refer to "People living with COVID-19" to align with existing person first language  and applying knowledge from other health care conditions with experiences of stigma .
What is Long Covid?
Long Covid has been preliminarily defined by The National Institute for Health and Care Excellence (NICE), the Scottish Intercollegiate Guidelines Network, and the Royal College of General Practitioners, as the presence of signs and symptoms that develop during or following an infection consistent with COVID-19 which continue for 12-weeks or more and are not explained by an alternative diagnosis. This includes both ongoing symptomatic COVID-19 (from 4 to 12 weeks) and "Post-COVID Syndrome" (12-weeks or more) .
The rapid and dynamic review of Long Covid evidence by the National Institute for Health Research (NIHR) suggests that Long Covid may be made up of 4 phenotypes :
- post-intensive care
- post-viral fatigue
- permanent organ damage
- long-term COVID
Consensus has not yet been reached on a Long Covid case definition , however attempts have been made to characterise Long Covid as prolonged with multi-system involvement and significant disability .
Long Covid Symptoms
Long Covid usually presents as clusters of symptoms, often overlapping, which can fluctuate and change over time and can affect any system in the body . Long Covid can include a range of 205 different signs and symptoms across body systems including but not limited to: pulmonary, cardiovascular, gastrointestinal, reproductive, genitourinary, endocrine, renal, dermatologic, musculoskeletal, neurological, neuropsychiatric, immunological, ophthalmic, and audiological . A list of common Long Covid symptoms is provided by The National Institute for Health and Care Excellence (NICE).
The most common Long Covid symptom is fatigue . The most frequently reported Long Covid symptoms after 6 months include fatigue, post-exertion malaise, and cognitive dysfunction . The multidimensional, episodic and often unpredictable nature of Long Covid has been described as "relapsing and remitting" , whereby 86% of people with Long Covid report relapses over 7 months, with physical activity, stress, exercise and mental activity being the most common triggers of relapses . The trajectory of Long Covid is heterogenous with some improving over time, some worsening and others stable, with many experiencing ongoing fluctuating symptoms after 6 months .
Long Covid Prevalence
Estimating the prevalence of Long Covid symptoms poses several challenges due to current lack of consensus definition and limited data collection in national surveys. The COVID-19 Infection Survey  is a nationally representative sample of the UK community population, from which it is has been estimated that around 1 in 5 people exhibit Long Covid symptoms for 5 weeks or longer, and around 1 in 10 exhibit Long Covid symptoms for 12 weeks or longer .
The aetiology and pathophysiological causes of Long Covid symptoms remains unknown, due to insufficient evidence. Initial hypothesis include: viral persistence , continued hyperactive immune response , cellular metabolic dysfunction , auto-antibodies , and organ impairment . More research is required.
Long Covid Management
The National Institute for Health and Care Excellence (NICE) published a rapid guideline on managing Long Covid , which covers identifying, assessing and managing Long Covid across all health care settings for adults, children and young people who have ongoing symptoms 4 weeks or more after the start of acute COVID-19. The novel nature of Long Covid has resulted in urgent calls for more research to fill existing gaps in knowledge . Co-designed quality standards for Long Covid services are proposed with potential patient care pathway model, highlighting equity and ease of access, minimal patient care burden, clinical responsibility, a multidisciplinary and evidence-based approach, and patient involvement .
The National Institute for Health Research (NIHR) has encouraged the use of the International Classification of Functioning Disability and Health (ICF) to provide a framework and standard language for the description of health and health-related state, due to current insufficient evidence to provide guidance . The ICF has been operationalised into the ICF Browser, ICF Checklist, and World Health Organization Disability Assessment Schedule (WHODAS) 2.0.
Some studies have performed a level of functional assessment, including "Post-COVID-19 Functional Status Assessment" (PCFS) , "COVID-19 Yorkshire Rehabilitation Scale" (C19-YRS), "Core Outcome Measure for Recovery" , sit-to-stand tests  , gait speed tests, modified Rankin Score , EuroQOL EQ-5D-5L , and SF-36 questionnaire .
It may be suitable to assess for post-exertion malaise  using measurement tools such as the DePaul Symptom Questionnaire . People living with Long Covid report post-exertion malaise , and the presence of this symptom would suggest exercise is not a safe rehabilitation intervention .
Management / Interventions
There is currently insufficient evidence on safe and effective interventions for management of Long Covid symptoms and impairments or disability.
The National Institute for Health and Care Excellence (NICE) has cautioned against the use of graded exercise therapy (GET) for managing post-viral fatigue, in response to draft guidance updates on the management of Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) . Substantial concerns exist regarding the potential for harm in respect to GET as an intervention for ME/CFS . Post-exertion malaise is a symptom experienced by people living with ME/CFS , and is characterised as the worsening of symptoms by exertion including physical, cognitive and emotional activities , which would prohibit exercise interventions. Among a sample of 3,762 people living with Long Covid, post-exertion malaise was reported by 72.2%, plus exercise is a common trigger for symptom relapses  warranting caution with exercise as a rehabilitation intervention for Long Covid and people living with COVID-19.
Groups representing people living with Long Covid have advocated for a risk stratification approach to exercise as a rehabilitation intervention. A focus is needed on assessing and excluding post-exertion malaise , plus screening for potential cardiac involvement  due to 32% prevalence of cardiac impairment among a young and low-risk population of people living with Long Covid and persistent symptoms .
The National Health Service (NHS) provides free online self-management rehabilitation for people recovering from COVID-19 called "Your COVID Recovery".
Mount Sinai Long Covid Recovery programme provides free online breath-work for Long Covid called "STASIS".
The National Institute for Health Research (NIHR) recently funded a research award for the Rehabilitation Exercise and psycholoGical support After covid-19 InfectioN (REGAIN) study .
Activity management or pacing is likely to be a safe and effective intervention for managing fatigue and post-exertion malaise. Heart rate monitoring is likely to be a safe and effective intervention for managing fatigue and post exertion malaise. Useful resources on pacing and heart rate monitoring are provided below:
- Royal College of Occupational Therapy (RCOT): "Post viral fatigue and energy conservation"
- Royal College of Occupational Therapy (RCOT): "How to manage post-viral fatigue after COVID-19 - Practical advice for people who have been treated in hospital"
- Royal College of Occupational Therapy (RCOT): "How to manage post-viral fatigue after COVID-19 - Practical advice for people who have recovered at home"
- Royal College of Occupational Therapy (RCOT): "How to conserve your energy"
- Workwell Foundation & Dialogues ME/CFS: "Activity and Energy Management – Pacing"
- PhysioForME: "Pacing"
- Sheffield Hallam University Advanced Wellbeing Research Centre (AWRC): "Fatigue" Video 1, Video 2, Video 3, Video 4
- ME Action: "Pacing and management guide for ME/CFS"
- Action for ME: "Pacing for people with M.E. A detailed guide to managing energy, rest and activity for adults with mild/moderate M.E."
- Emerge Australia: "Pacing"
- PhysioForME: "Heart Rate Monitoring"
- PhysioForME: "Heart Rate Monitoring Podcast"
- ME Association: "Assessing Post Exertion Malaise (PEM)" page 6
Peer support involves people sharing knowledge, experience, or practical help with each other, often when living with the same or similar health conditions. Many online Long Covid peer support groups have been established for people living with Long Covid. These are safe spaces for people living with Long Covid to access peer support, therefore mutual respect and confidentiality is requested. Many of these groups have outputs to share valuable information with allies. Long Covid groups include:
- Long Covid Physio
- Body Politic - Twitter
- Long Covid Support - Twitter
- Long Covid SOS - Twitter
- Long Covid Kids - Twitter
- Long Covid Italia
- Apres J20 (France) - Twitter
- Long Covid Wales
- Long Covid Scotland - Twitter
- Long Covid Netherlands
- Long Covid Spain
- Covid Persistente Espana
- Long Covid Valencia
- Long Covid Switzerland
- COVID-19 Longhauler Advocacy Project (USA)
- Long Covid Minnesota
- Utah COVID-19 Long Haulers
- CanCovid (Canada) - Twitter
- Long Covid Indonesia
- Covid Persistente Mexico Comunidad Solidaria
- COVID-19 Patient Stories / Recovery Collective - Twitter
- Patient led research for Long Covid - Twitter
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