Long Covid: The emergence of the Parallel Pandemic
Please note: this was written in November and December of 2020.
Severe Acute Respiratory Syndrome CoV2 (SARS-CoV-2) is an acute respiratory and vascular disease, neurotropic in nature and first reported in the human population in late December 2019. On 31st January 2020 the World Health Organisation declared a Public Health Emergency of International Concern, and by February 6, 2020 the virus had expanded to 25 countries with a total of 28,276 confirmed cases and 565 deaths globally (WHO.Int. 23 January 2020). A global pandemic ensued, with millions of cases worldwide (Wu, Chen and Chan, 2020), and this highly infectious, pathogenic novel virus was officially named Coronavirus Disease-2019 (Covid-19) on February 11, 2020.
Clinical Presentation & Symptoms
The working case definition for viral testing of Covid-19 was severe acute respiratory illness with fever and respiratory symptoms, such as cough and shortness of breath (Vetter et al., 2020). This strategy captures typical symptomatic presentation, but fails to identify unusual manifestations, such as patients without respiratory symptoms or only very mild symptoms. In China one widely cited study concluded that up to 86% of cases may have been missed (Li et al., 2020).
In attempting to assimilate ongoing evidence of symptoms a Symptom Study app was developed by Kings College London (Symptom Study App, 2020) with participants from the UK, US and Sweden. Over 4 million users logged their daily health and potential symptoms of Covid-19, and evidence emerged indicating a multisystem disease (Barker-Davies et al., 2020) with an ongoing theme of symptoms arising in one physiological system and abating, only to then arise in a different system (NIHR, 2020).
Symptoms of Covid-19 usually appear after an incubation period of approximately 5 days, and are most commonly: fever, cough, dyspnoea and headache. Clinical signs include low levels of lymphocytes or white blood cells (lymphopenia) and elevated levels of serum Tumour Necrosis Factor (TNF) and Interleukin-6 (IL6), a cytokine produced in response to infection (Tanaka et al., 2014). Elevated inflammatory markers are clinical hallmarks of advanced infection and in severe cases patients may develop pneumonia, acute respiratory distress, acute cardiac problems and multi-organ failure. Pulmonary damage contributes to Acute Respiratory Distress Syndrome (ARDS) which is the main cause of death in Covid-19 patients (Wu & McGoogan, 2020). We can conclude that disease severity is due not only to the viral infection, but also the host response (Erener, 2020).
It is important to acknowledge health disparities, and research shows that acute Covid-19 disproportionately affects certain groups in society. Age is strongly associated with risk of severe disease, alongside underlying health conditions such as hypertension and obesity (Docherty et al. 2020). These established risk factors are characterised by pre-existing endothelial dysfunction (Li et al., 2019) and high glucose levels are known to increase endothelial dysfunction and reduce Nitric Oxide (NO) bioavailability (Erener, 2020). Diabetics are therefore at increased risk, specifically newly diagnosed diabetics are at higher risk than pre-existing populations, who medicate to control glucose levels (Hoshiyama et al., 2004).
Males are 40% more at risk of dying from Covid-19 than women (Peckham et al., 2020) with findings indicating low testosterone levels in men are “associated with increased mortality” (Rastrelli et al., 2020). Health care workers are more at risk due to viral load, with studies indicating a 3.4-fold higher risk (Nguyen et al., 2020).
The Emergence of Long Covid: The Parallel Pandemic
Widespread perception was that most people infected with Covid-19 either die, are admitted to hospital or experience mild to moderate illness and recover within two weeks without requiring treatment (NIHR, 2020). However, since May 2020 increasing attention has been given to the experiences of people with Covid-19 symptoms persisting for 4 weeks or more. According to the Office for National Statistics (ONS) an estimated 186,000 people in England currently have Covid-19 symptoms 5-12 weeks after initial acute infection, with one in five experiencing symptoms that persist for 5 weeks or more, and one in ten continuing to experience symptoms for 12 weeks or longer (ONS, 2020).
“Evidence shows that survivors are likely to have significant ongoing health problems, including breathing difficulties, enduring tiredness, reduced muscle function, impaired ability to perform vital everyday tasks, and mental health problems such as post-traumatic stress disorder, anxiety, and depression,”
NHS England, 2020
Early research (Carfì, Bernabei and Landi, 2020) indicates that 87% of people discharged from hospital experienced at least one symptom 60 days after the onset of the virus with 40% reporting reduced quality of life. These findings were echoed by Clinicians at the Royal Free London and University College Hospitals NHS Trust (UCLH) demonstrating that following discharge many continue to experience ongoing symptom burden and changes to lung functions (Mo et al., 2020).
As of November 2020, The Symptom Study App team at Kings College London, released data predicting those most at risk of Long Covid:
- 10% of 18-49-year olds
- 22% of over 70s
- Women are 50% more likely to suffer than men (but only in the 18-59 age category)
- Those with slightly higher than average BMI
- People with pre-existing asthma
- Those who suffered a greater number of different symptoms in the first week of illness
“There’s certainly a group of Long Covid sufferers that have this multi-system immune–like disease, where they get gastrointestinal problems, skin rashes, nerve problems and brain fog – so the whole body is involved rather than just one bit. Probably, the immune system is working differently in such people, which may manifest as symptoms in multiple body systems being experienced from week one”. Professor Tim Spector, KCL, 2020.