US National Academies of Sciences, Engineering, and Medicine issues Long COVID definition

On 11th June 2024, the US’s National Academies of Sciences, Engineering, and Medicine released a report urging federal, state and local authorities, educators, insurance companies, employers, benefit agencies healthcare professionals, and researchers to adopt adopt a new definition of Long COVID (LC). According to the 2024 NASEM definition of long COVID the illness “…… is an infection-associated chronic condition which occurs after SARS-CoV-2 infection and is present for at least 3 months as a continuous, relapsing and remitting, or progressive disease state that affects one or more organ systems.” 

The definition is indeed broad with people able to present with :

  • single or multiple symptoms, such as shortness of breath, cough, persistent fatigue, post-exertional malaise, difficulty concentrating, memory changes, recurring headache, lightheadedness, fast heart rate, sleep disturbance, problems with taste or smell, bloating, constipation, and diarrhoea.
  • single or multiple diagnosable conditions, such as interstitial lung disease and hypoxemia, cardiovascular disease and arrhythmias, cognitive impairment, mood disorders, anxiety, migraine, stroke, blood clots, chronic kidney disease, postural orthostatic tachycardia syndrome (POTS) and other forms of dysautonomia, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), mast cell activation syndrome (MCAS), fibromyalgia, connective tissue diseases, hyperlipidemia, diabetes, and autoimmune disorders such as lupus, rheumatoid arthritis, and Sjögren’s syndrome.

Important features are:

  • LC can follow asymptomatic, mild, or severe COVID (SARS-CoV-2) infection. Previous infections may have been recognised or unrecognised. No laboratory confirmation or other proof of the initial infection with COVID is required.
  • LC can be continuous from the time of acute COVID infection or can be delayed in onset for weeks or months following what had appeared to be full recovery from acute infection. Symptoms to be present for over 3 months.
  • LC can affect children and adults, regardless of health, disability, or socio-economic status, age, sex, gender, sexual orientation, race, ethnicity, or geographic location.
  • LC can exacerbate pre-existing health conditions or present as new conditions.
  • LC can range from mild to severe. It can resolve over a period of months or can persist for months or years.
  • LC can be diagnosed on clinical grounds. No biomarker currently available demonstrates conclusively the presence of LC.
  • LC can impair individuals’ ability to work, attend school, take care of family, and care for themselves. It can have a profound emotional and physical impact on patients and their families and carers.


The definition does not list any symptoms or conditions as being required or any as being exclusionary. While some examples of specific symptoms are included in the definition, they are not meant to be exhaustive or to dismiss the significance of other symptoms or conditions. The Report mentions, post-exertional malaise, persistent fatigue, concentration/memory issues, headaches, lightheadedness, sleep disturbance, gastrointestinal disturbances, taste and smell issues amongst others. A complete enumeration of signs, symptoms, and diagnosable conditions of Long COVID would have more than 200 entries.

What is also clear is that the definition is intended to be revised and updated as science’s state of knowledge improves. It does warn that as a large proportion of the population has been infected with COVID-19 finding uninfected control groups will become an increasing challenge in conducting research.

Items which may trigger re-evaluation of the definition include –

  • Symptoms and organ damage that distinguish Long COVID from healthy people and other medical conditions.
  • Onset and duration, including delayed onset of Long COVID after an ostensible period of recovery from acute infection.
  • Recovery trajectory and natural history over longer periods of time.
  • Presence and prevalence of co-morbid conditions.
  • Biomarker(s) to diagnose Long COVID.
  • Risk factors for Long COVID.
  • Prevalence and outcomes of Long COVID by sex, gender, race, ethnicity, socioeconomic status, and other factors.
  • New treatment and management options that could potentially affect the sensitivity threshold and elements of the definition

Professor Lenny Jason has criticised the work as being overly broad and risks faling those affected in the long-run. He indicates that the current draft has good sensitivity, meaning that everyone who has long COVID will probably be included but has poor specificity i.e. in the ability of a test to correctly identify people without the disease. He urges that learnings are taken from mistakes in ME/CFS research definitions.

We must learn from past experiences with other post-viral illnesses. Patients with ME/CFS have had to endure the losses of a debilitating illness and then be re-traumatized by the reactions of healthcare workers, friends, and even family members to their disease. This is due, in part, to an empathy breakdown causing stigma. Because 20% of the general population experiences fatigue, many feel their experience of illness is comparable to ME/CFS; so, an unwitting conscious or unconscious bias is that if they can cope with fatigue, why can’t those with ME/CFS?”

Prof L Jason – Here’s What is Wrong with the National Academies’ Long COVID Definition

Basically, Prof Jason is concerned

that a person can meet the proposed long COVID criteria by merely having one symptom that is not a burden to the person or does not have any negative impact on the person’s functioning. If a person has trivial pain in the toe for 3 months following COVID infection, with no negative consequences to the person’s functioning or quality of life, that person would still be eligible for a long COVID diagnosis. The failure to list any thresholds of frequency or severity of symptoms, so that the symptoms are not trivial, has major consequences for an infection that is as widespread as COVID……

…… if the vast majority of citizens are eligible for a long COVID diagnosis given their prior infection, and the threshold criteria for being diagnosed is so minimal, then it is possible that the prevalence of long COVID could increase exponentially.

Even the recommendation to re-visit the recommendation echoes prior failures. In 2015 the National Academies made a recommendation for a reconvening of the ME/CFS case definition group within 5 years, it never occurred. The 2015 process will be remembered for the suggestion of a new name for ME/CFS – Systemic Exertion Intolerance Disease – and the 2015 (then) Institute of Medicine definition.

That 2015 National Academies report also made the unfortunate recommendation to have almost no exclusionary illnesses for ME/CFS, and as a result of this broadened criteria, prevalence rates are estimated to have increased 2.8 times Furthermore, while the new ME/CFS case definition was designed to be used for clinical purposes, it is now used for research purposes. This can lead to inclusion of trial participants who may not actually have ME/CFS, skewing research findings. We can expect a similar pattern to occur with the newly proposed long COVID case definition.

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