Long COVID

Long COVID, also known as post-COVID-19 syndrome, post-acute sequelae of COVID-19 (PASC), chronic COVID syndrome (CCS) and long-haul COVID, is a condition characterized by long-term sequelae—appearing or persisting after the typical convalescence period—of coronavirus disease 2019 (COVID-19). Long COVID can affect nearly every organ system with sequelae including respiratory system disorders, nervous system and neurocognitive disorders, mental health disorders, metabolic disorders, cardiovascular disorders, gastrointestinal disorders, malaise, fatigue, musculoskeletal pain, and anemia. A wide range of symptoms are commonly discussed, including fatigue, headaches, shortness of breath, anosmia (loss of smell), parosmia (distorted smell), muscle weakness, low fever and cognitive dysfunction.

The exact nature of symptoms and number of people who experience long-term symptoms is unknown and varies according to the population being studied, the definition used, and the time period used in the study. A preliminary survey by the UK Office for National Statistics estimated that approximately 10% of people who tested positive for SARS-CoV-2 experienced one or more symptoms for longer than 12 weeks.

While studies into various aspects of long COVID are under way, as of January 2021, the definition of the illness is still unclear and it is too early to draw conclusions on the mechanism. Health systems in some countries or jurisdictions have been mobilized to deal with this group of patients by creating specialized clinics and providing advice. Nonetheless, the illness is not well-characterized, has no understood mechanism nor fixed diagnostic criteria, and therefore is considered an idiopathic disease, and a diagnosis of exclusion.

While long COVID is observed after COVID-19 infection, it has not been reported after COVID-19 vaccination, with over 100,000 participants included in vaccine trials as of December 2020.

Terminology and definitions

Long COVID is a patient-created term which was reportedly first used in May 2020 as a hashtag on Twitter by Elisa Perego, an archaeologist at University College London.

Long COVID has no single, strict definition. It is normal and expected that people who experience severe symptoms or complications such as post-intensive care syndrome or secondary infections will naturally take longer to recover than people who had mild illness and no such complications. This natural variation can make it difficult to determine whether a specific individual's set of ongoing symptoms represent a fundamentally normal, if long, convalescence, or long COVID. One rule of thumb is that long COVID represents symptoms that have been present for longer than two months, though there is no reason to believe that this choice of cutoff is specific to infection with the SARS-CoV-2 virus.

British definition

The British National Institute for Health and Care Excellence (NICE) divides COVID-19 into three clinical case definitions:

• acute COVID-19 for signs and symptoms during the first 4 weeks after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the first, and the other two are for
• new or ongoing symptoms 4 weeks or more after the start of acute COVID-19, both of which it includes under the term 'long COVID', and divides into:
  • ongoing symptomatic COVID-19 for effects from 4 to 12 weeks after onset, and
  • post-COVID-19 syndrome for effects that persist 12 or more weeks after onset.

NICE describes the term long COVID, which it uses "in addition to the clinical case definitions", as "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)".

NICE defines post-COVID-19 syndrome as "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".

U.S. definition

In February 2021, the National Institutes of Health said symptoms of Long COVID can include fatigue, shortness of breath, "brain fog", sleep disorders, intermittent fevers, gastrointestinal symptoms, anxiety, and depression. Symptoms can persist for months and can range from mild to incapacitating, with new symptoms arising well after the time of infection. NIH Director Francis Collins said the condition can be collectively referred to as Post-Acute Sequelae of SARS-CoV-2 infection (PASC).

Incidence

Some reports of long-term illness after infection appeared early during the COVID-19 pandemic, including in people who had a mild or moderate initial infection as well as those who were admitted to hospital with more severe infection. In a 4-year survey following SARS in Hong Kong, 42.5% of survivors reported at least one diagnosable psychiatric disorder ranging from post-traumatic stress disorders, depression, and chronic fatigue.

As of January 2021, the precise incidence was unknown. The incidence declines over time, as many people slowly recover. Some early studies suggested that between 20% and 33% of people with COVID-19 experienced symptoms lasting longer than a month. A telephone survey in the US in the first half of 2020 showed that about 35% of people who had tested positive for SARS-CoV-2 experienced a range of symptoms that lasted longer than three weeks. As of December 2020, the Office of National Statistics in the UK estimated that, of all people with a positive test for SARS-CoV-2, about 21% experienced symptoms for longer than five weeks, and about 10% experienced symptoms for longer than 12 weeks.

Some studies have suggested that some children experience lingering symptoms of SARS-CoV-2 infection.

Although anyone who gets infected can develop long COVID, people who become so sick that they require hospitalization take longer to recover. A majority (up to 80%) of those who were admitted to hospital with severe disease experience long-term problems including fatigue and shortness of breath (dyspnoea). Patients with severe initial infection, particularly those who required mechanical ventilation to help breathing, are also likely to suffer from post-intensive care syndrome following recovery. A study of patients who had been hospitalised in Wuhan found that the majority still had at least one symptom after six months. Patients who had been more severely ill still showed severe incapacity in lung function. Among the 1733 patients who had been discharged from hospital and followed up about six months later, the most common symptoms were fatigue or muscle weakness (63%), sleep difficulties (26%), and anxiety or depression (23%).

Some people suffer long-term neurologic symptoms despite never having been hospitalized for COVID-19; the first study of this population was published in March 2021. Most frequently, these non-hospitalized patients experienced "prominent and persistent 'brain fog' and fatigue that affect their cognition and quality of life."

In January 2021, a study in the UK reported that 30% of recovered patients were readmitted to hospital within 140 days, and 12% of the total died. Many patients had developed diabetes for the first time, as well as problems with heart, liver and kidney problems. The mode of insulin failure was at that point unknown.

In March 2021, the Indonesian Doctors Association, in a survey of 463 people, suggested that 63.5% of respondents self-reported lingering symptoms after SARS-CoV-2 infection. The exact set of symptoms was not specified, however, according to the article, fatigue and cough were the most commonly reported symptoms, followed by muscle pain and headache.

In May 2021, a global systematic review led by researchers at Stanford University reported that a wide variety of symptoms persisted in more than 70% of COVID-19 patients months after recovering from the initial phase of the disease. Most patients in this study were previously hospitalized. The most common lingering symptoms included shortness of breath, fatigue, and sleep disorders. In total, the study reported 84 clinical signs or symptoms, including loss of taste and smell, cognitive disorders such as memory loss and difficulty concentrating, depression, and anxiety.

Cause

It is currently unknown why most people recover fully within two to three weeks and others experience symptoms for weeks or months longer. Although the exact processes that cause long COVID remain unknown, a number of mechanisms have been suggested.

A March 2021 review article cited the following pathophysiological processes as the predominant causes of long COVID:

• direct toxicity in virus infected tissue, especially the lungs
• ongoing inflammation due to post-infection immune system dysregulation
• vascular injury and ischemia caused by virus induced hypercoagulability and thromboses
• impaired regulation of the renin-angiotensin system related to the effect of SARS-CoV-2 on ACE2 bearing tissue

In October 2020, a review by the United Kingdom's National Institute for Health Research hypothesized that ongoing long COVID symptoms may be due to four syndromes:

• permanent damage to the lungs and heart,
• post-intensive care syndrome,
• Post-viral fatigue, sometimes regarded as the same as Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS), and
• continuing COVID-19 symptoms.

Other situations that might cause new and ongoing symptoms include:

• the virus being present for a longer time than usual, due to an ineffective immune response;
• reinfection (e.g., with another strain of the virus);
• damage caused by inflammation and a strong immune response to the infection;
• physical deconditioning due to a lack of exercise while ill; and
• post-traumatic stress or other mental sequelae, especially in people who had previously experienced anxiety, depression, insomnia, or other mental health difficulties.

Similarities to other syndromes

Long COVID is similar to post-Ebola syndrome and the post-infection syndromes seen in chikungunya and the infections that appear to trigger ME/CFS, and the pathophysiology of long COVID may be similar to these other conditions. Some long COVID patients in Canada have been diagnosed with myalgic encephalomyelitis/chronic fatigue syndrome, a "debilitating, multi-system neurological disease that is believed to be triggered by an infectious illness in the majority of cases". Lucinda Bateman, a specialist in ME/CFS in Salt Lake City in the US believes that the two syndromes are identical. There is need for more research into ME/CFS; Anthony Fauci, chief medical adviser to the US government, said that COVID-19 is a "well-identified etiologic agent that should be very helpful now in getting us to be able to understand [ME/CFS]”.

Risk factors

According to a King's College London study initially posted on 21 October 2020 risk factors for long COVID may include:

• Age – particularly those aged over 50
• Excess weight
• Asthma
• Reporting more than five symptoms (e.g. more than cough, fatigue, headache, diarrhoea, loss of sense of smell) in the first week of COVID-19 infection; five is the median number reported

Women are less likely to develop severe acute COVID but more likely to develop long COVID than men. Some research suggests this is due primarily to hormonal differences, while other research points to other factors, including chromosomal genetics, sex-dependent differences in immune system behavior, and non-biological factors may be relevant.

In children

A study in Italy, which analyzed 129 children under the age of 18, examined health data obtained via a questionnaire between September 2020 and 1 January 2021. 53% of the group experienced COVID-19 symptoms more than 120 days after their diagnosis. Symptoms included chest tightness and pain, nasal congestion, tiredness, difficulty concentrating and muscle pain. A case report of 5 children in Sweden also reported symptoms (fatigue, heart palpitations, dyspnoea, headaches, muscle weakness and difficulty concentrating) persisting for 6–8 months after diagnosis.

Health system responses

United States

Dr. Anthony S. Fauci has described long-term COVID-19 as “...a phenomenon that is really quite real and quite extensive,” but also said that the number of cases is unknown.

On 23 February 2021, National Institutes of Health Director Francis Collins announced a major initiative to identify the causes and ultimately the means of prevention and treatment of people who are suffering from long COVID. Part of this initiative includes the creation of the COVID-19 Project, which will gather data on neurological symptoms associated with PASC.

On 28 April 2021, the Subcommittee on Health of the U.S. House of Representatives' Committee on Energy and Commerce held a hearing about long COVID.

Australia

In October 2020, a guide published by the Royal Australian College of General Practitioners (RACGP) says that ongoing post-COVID-19 infection symptoms such as fatigue, shortness of breath and chest pain will require management by GPs, in addition to the more severe conditions already documented.

United Kingdom

In Britain, the National Health Service set up specialist clinics for the treatment of long COVID. The four Chief Medical Officers of the UK were warned of academic concern over long COVID on 21 September 2020 in a letter written by Trisha Greenhalgh published in The BMJ signed by academics including David Hunter, Martin McKee, Susan Michie, Melinda Mills, Christina Pagel, Stephen Reicher, Gabriel Scally, Devi Sridhar, Charles Tannock, Yee Whye Teh, and Harry Burns, former CMO for Scotland. In October 2020, NHS England's head Simon Stevens announced the NHS had committed £10 million to be spent that year on setting up long COVID clinics to assess patients' physical, cognitive, and psychological conditions and to provide specialist treatment. Future clinical guidelines were announced, with further research on 10,000 patients planned and a designated task-force to be set up, along with an online rehabilitation service – "Your Covid Recovery". The clinics include a variety of medical professionals and therapists, with the aim of providing "joined-up care for physical and mental health”.

The National Institute for Health Research has allocated funding for research into the mechanisms behind symptoms of Long COVID.

In December 2020, University College London Hospitals (UCLH) opened a second Long Covid clinic at the National Hospital for Neurology and Neurosurgery for patients with post-Covid neurological issues. The first clinic had opened in May, primarily focused on respiratory problems, but both clinics refer patients to other specialists where needed, including cardiologists, physiotherapists and psychiatrists. By March 2021 there were 69 long covid clinics in the English NHS. mostly focussing on assessing patients, with more planned to open. There were fears that community rehabilitation services did not have capacity to manage large numbers of referrals.

On 18 December 2020, the National Institute for Health and Care Excellence (NICE), the Royal College of General Practitioners (RCGP) and the Scottish Intercollegiate Guidelines Network (SIGN) published a guide to the management of Long COVID.

South Africa

In October 2020, the DATCOV Hospital Surveillance Department of the National Institute for Communicable Diseases (NICD) looked into a partnership with the International Severe Acute Respiratory and emerging Infection Consortium (ISARIC) in order to conduct clinical research into the impact PASC may have within the South African Context. As of 30 January 2021, the project has yet to receive ethical approval for the commencement of data collection. Ethics approval was granted on 3 February 2021 and formal data collection began on 8 February 2021.

Public response

Some people experiencing long COVID have formed groups on social media sites. There is an active international long COVID patient advocacy movement which includes research led by patients themselves. In many of these groups, individuals express frustration and their sense that their problems have been dismissed by medical professionals.

List of symptoms

Symptoms reported by people with long COVID include:

• Extreme fatigue
• Long lasting cough
• Muscle weakness
• Low grade fever
• Inability to concentrate (brain fog)
• Memory lapses
• Changes in mood, sometimes accompanied by depression and other mental health problems
• Sleep difficulties
• Headaches
• Joint pain
• Needle pains in arms and legs
• Diarrhoea and bouts of vomiting
• Loss of taste and smell
• Sore throat and difficulties swallowing
• New onset of diabetes and hypertension
• Heartburn (gastroesophageal reflux disease)
• Skin rash
• Shortness of breath
• Chest pains
• Palpitations
• Kidney problems (acute kidney injury, and chronic kidney disease)
• Changes in oral health (teeth, saliva, gums)
• Anosmia (lack of sense of smell)
• Parosmia (change in sense of smell)
• Tinnitus
• Blood clotting (deep vein thrombosis and pulmonary embolism)

See also

• Post viral cerebellar ataxia – clumsy movement appearing a few weeks after a viral infection
• Post-Ebola virus syndrome – symptoms that persist after recovering from Ebola
• Post-polio syndrome – delayed reaction appearing years after acute polio infection resolves
• COVID-19: neurologic and psychiatric symptoms – both acute and chronic neurologic, psychiatric, olfactory and mental health conditions
• Multisystem inflammatory syndrome in children – pediatric comorbidity from COVID-19

Further reading

• With guests Dr Ian Frayling (Ireland), Dr Nathalie Macdermott (Great Ormond Street), and Dr Nathalie Macdermott (Scotland).

External links

• Long Covid on YouTube (21 October 2020). – UK Government film about long COVID.