What is Long COVID?

Whilst COVID-19 symptoms subside in the majority of patients after a couple of weeks, there is an emerging group of people who suffer long-term effects of the infection.

This newly emerging condition has been dubbed long COVID and describes people who experience prolonged symptoms for 4 weeks or longer. Affecting about one-in-five people who test positive for COVID-19, the implications and consequences of the syndrome present a growing global health concern.

Fatigue and breathlessness are common long-term effects of COVID-19. Image Credit: Image Point Fr / Shutterstock.com

The majority of people who become infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) will go on to develop mild to moderate COVID-19 and will recover fully in 2-4 weeks.

A small proportion of people, currently thought to be approximately 20% of those infected, continue to suffer with symptoms for weeks or months post-infection. In the UK, the Royal College of General Practitioners (RCGP) and the National Institute for Health and Care Excellence (NICE) use the following clinical definitions to distinguish the initial infection and disease at different time points:

Acute COVID-19: Symptoms lasting up to 4 weeks.
Ongoing symptomatic COVID-19: Symptoms lasting between 4 and 12 weeks.
Post-COVID-19 syndrome: Symptoms that develop during or after SARS-CoV-2 infection that last over 12 weeks and are not explained by an alternative diagnosis.

Although experiencing symptoms for longer than 4 weeks only appears to affect about one-fifth of those who develop COVID-19, given the sheer number of total infections, long COVID will have a profound effect on individuals and healthcare systems.

In August 2020, the British Medical Association issued a press release to draw attention to the prevalence of long COVID and outlining the long-term risk that SARS-CoV-2 presents to the National Health Service, healthcare staff and patients. Other health institutions such as the World Health Organisation (WHO) and Centre for Disease Control and Prevention (CDC) have also brought attention to the long term effects of COVID-19.

What are the symptoms of ongoing symptomatic COVID-19 and post-COVID-19 syndrome?

Symptoms after acute COVID-19 (long COVID) are wide-ranging and appear to vary widely from person to person. However, the most commonly reported symptoms include:

Respiratory symptoms including breathlessness and cough,
Cardiovascular symptoms including chest tightness and pain and palpitations,
Neurological symptoms such as headache, dizziness, peripheral neuropathy, cognitive disturbance and insomnia,
Muscular-skeletal symptoms including joint and muscle pain
Generalized symptoms including fatigue, pain and fever.

One recently published study analyzed data collected as part of a COVID-19 follow-up clinical service. The service aimed to assess a range of symptoms in people who had been admitted to hospital with COVID-19, 4-6 weeks following their discharge.

From their sample of over 350 patients, the researchers found that 54% experienced ongoing and frequent breathlessness, 34% continued to report a persistent cough and 69% reported ongoing fatigue. Of the sample, 15% reached the clinical threshold for a diagnosis of depression.

In addition to self-reported ongoing and chronic symptoms, physical tests showed that 9% had a deteriorated chest radiograph, suggestive of possible lung fibrosis. 30% had elevated d-dimer, indicative of blot clots, and 9% showed elevated inflammatory biomarkers.

An Italian study that followed up COVID-19 hospital patients 8 weeks following discharge found that 87% reported persistence of at least one symptom, most commonly breathlessness or fatigue.

Studies are suggesting that age is positively correlated with long COVID. Image Credit: Bonsales / Shutterstock.com

Predictors of long COVID

Research into the attributes and risk-factors of long COVID are in their infancy. Whilst reports of the syndrome are increasing, there is a paucity of knowledge regarding its prevalence and predictive possibility. One study, currently in preprint and therefore not yet peer-reviewed, used a prospective cohort design to compare patients with symptoms persisting over 10 days versus 28 days.

The researchers found that symptom duration was positively associated with age. Approximately 10% of adults 49 or younger sampled continued to experience symptoms at 28 days, but this rose to 22% when adults were aged 70 and above. Initial severity of COVID-19 symptoms also predicted a propensity towards long COVID: those with symptoms at 28 days were significantly more likely to have required hospital assessment. The only pre-existing condition that was associated with long COVID was asthma, although it was more likely in those with a higher body mass index.

The authors also found that developing five specific symptoms during the first week of COVID-19 symptom onset was most predictive of developing long COVID. These included: fatigue, headache, breathlessness, hoarse voice and muscular pain.

Although more research into long COVID is required, this information could help to determine those at the highest risk of long-term symptoms, design early-intervention trials and help target healthcare resources in the future.

References

British Medical Association (2021). BMA Survey Reveals Impact Of Long-Term Covid-19 Symptoms On Patients And Doctors – BMA Media Centre – BMA. [online] Available at: <https://www.bma.org.uk/bma-media-centre/bma-survey-reveals-impact-of-long-term-covid-19-symptoms-on-patients-and-doctors> [Accessed January 2021].
Carfì, A., Bernabei, R., Landi, F., & Gemelli Against COVID-19 Post-Acute Care Study Group (2020). Persistent Symptoms in Patients After Acute COVID-19. JAMA, 324(6), 603–605. https://doi.org/10.1001/jama.2020.12603
Mandal, S., Barnett, J., Brill, S. E., Brown, J. S., Denneny, E. K., Hare, S. S., Heightman, M., Hillman, T. E., Jacob, J., Jarvis, H. C., Lipman, M., Naidu, S. B., Nair, A., Porter, J. C., Tomlinson, G. S., Hurst, J. R., & ARC Study Group (2020). 'Long-COVID': a cross-sectional study of persisting symptoms, biomarker and imaging abnormalities following hospitalisation for COVID-19. Thorax, thoraxjnl-2020-215818. Advance online publication. https://doi.org/10.1136/thoraxjnl-2020-215818
National Institute of Health and Clinical Excellence (2021). [online] Available at: <https://www.nice.org.uk/guidance/ng188/resources/covid19-rapid-guideline-managing-the-longterm-effects-of-covid19-pdf-66142028400325> [Accessed January 2021].
Sudre, C.H., Murray, B., Varasavsky, T. et al. Attributes and predictors of Long-COVID: analysis of COVID cases and their symptoms collected by the Covid Symptoms Study App https://doi.org/10.1101/2020.10.19.20214494. This article is a preprint and has not been peer-reviewed

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What is Long COVID?