According to Office for National Statistics (ONS) estimates, as of 2 January 2022 around 1.3 million people in the UK, or 2.1 per cent of the population, have reported symptoms persisting more than four weeks after the first suspected COVID-19 infection, including 554,000 with symptoms lasting longer than a year. Fatigue is the commonest symptom, and 63 per cent of respondents have claimed that their symptoms have adversely affected their ability to perform daily activities. These estimates are based upon responses to the four-week-long Coronavirus (COVID-19) Infection Survey, which ended on 2 January.
Reports of long COVID symptoms are by no means unexpected. Persistent symptoms have previously been described in the aftermath of certain viral infections, long after the original causative organism has been eliminated. The best-known example is that of chronic fatigue syndrome (CFS), or myalgic encephalomyelitis (ME), which has been linked to infection with the Epstein-Barr virus and human herpes virus 6, although similar illnesses have followed other viral infections, such as with coronaviruses causing Severe Acute Respiratory Syndrome (SARS). In its most severe instances, CFS can produce debilitating tiredness and weakness, leading to inability to care for oneself and a state of long-term dependency.
The term long COVID refers to a variety of symptoms that continue for at least four to twelve weeks after the onset of either confirmed or probable COVID-19 infections, and for which there is no alternative explanation. Other names for the condition include post-COVID syndrome and post-acute sequelae of SARS Cov-2 (PASC). Prolonged symptoms after COVID-19 were first recognised by sufferers, as early as April 2020. They first coined the term long COVID, referred to themselves as “long-haulers”, and shared their experiences on social media platforms, in print media, and through patient support groups. The symptoms of these early victims were further explored in questionnaire surveys, a useful epidemiological tool, although prone to so-called recall bias.
Symptoms may either develop after complete recovery from acute COVID-19 or may persist after the initial illness, which itself may vary in severity from mild to severe. Many body systems can be affected, producing cardiovascular (chest tightness, palpitations, dizziness), respiratory (shortness of breath), neurological (memory loss, difficulty concentrating, headache), gastrointestinal (abdominal pain, diarrhoea), musculoskeletal (muscle and joint pain), psychiatric (anxiety, depression), and dermatological (skin rashes) symptoms, in addition to persistent loss of smell or taste. These symptoms may fluctuate over time, and cannot be explained by an alternative diagnosis. A review by the UK’s NIHR (National Institute for Health Research) has identified four major types of presentations of long COVID: post-viral chronic fatigue, fluctuating multi-system symptoms, lasting organ damage (lungs, kidneys, heart), and post-intensive care symptoms such as “brain fog” (cognitive impairment) and chronic shortness of breath. The natural history of long COVID, including its progression over time and the duration of symptoms before recovery, remains to be fully understood.
There is no universally accepted definition for long COVID, and there are no symptoms or combinations of symptoms that are unique to the condition. The diagnosis depends upon a combination of self-reported symptoms, an appropriate length of time since the onset of the acute episode of COVID-19, and the exclusion of alternative causes for these symptoms. On physical examination of sufferers, nothing abnormal may be found. There is no specific diagnostic laboratory or imaging test for long COVID, although in certain situations testing may yield useful information. For example, it has been reported recently by the four-centre EXPLAIN study in England that hyperpolarised xenon MRI scans, a highly specialised form of imaging, may show persistent and otherwise undetectable abnormalities in gas transfer in the lungs in patients with post-COVID breathlessness. The large majority of victims of long COVID no longer test positive for COVID-19, and are unable to infect others.
Some groups of people seem more likely to develop long COVID. Risk factors mentioned in medical publications include younger age (35 to 69 years), female sex, obesity, asthma, type 2 diabetes, and lower socio-economic status. QCovid has been developed as a risk assessment tool to help doctors determine the risk of long COVID for individual patients, while blood antibody measurements are being developed for the same purpose. Vaccination, on the other hand, may reduce the risk of long COVID by as much as half, without eliminating it altogether
The possible underlying reasons why some people develop long COVID symptoms have yet to be determined. It has been postulated that the virus may cause the host’s immune response to go into “overdrive”, triggering a self-perpetuating autoimmune response, in which newly-formed autoantibodies continue to attack host cells. It is also possible that, in some instances, either the virus or viral fragments lie dormant or latent, only to be reactivated at a later date.
There is no specific curative treatment for long COVID. Symptoms may be controlled by a number of different means, including peer group support, online help, complementary therapies, physiotherapy, psychotherapy (cognitive behavioural therapy), and occupational therapy. There is no proven drug treatment, and any prescribed medications are intended only to relieve symptoms. Sufferers can avail of specialist services, such as the Long COVID Service introduced by the NHS in England in October 2020, which provides access to long COVID clinics- these facilities which appear to be under-utilised at present.
The economic consequences of long COVID are likely to be significant, given the large numbers of people claiming post-COVID symptoms, which can affect their employment rights and their access to sick pay and benefit packages. In the UK, those with long COVID and unable to work as a result may qualify for Statutory Sick Pay, or for Universal Credit or Employment and Support Allowance if ineligible, and for additional Personal Independence Payments to assist with daily tasks of living.
Even as we continue to learn about long COVID, there are indications that some healthcare professionals, as well as employers, seem inclined to believe that many post-COVID symptoms are psychological in origin, lacking any demonstrable physical basis. It is far too premature to make any such judgements. We must be guided by the results of ongoing surveillance programmes and clinical trials, fully accepting that, at least for the moment, our knowledge of long COVID is both incomplete and imperfect.
Ashis Banerjee