Deborah Carr examines the long-term effects of coronavirus infection.

‘Long Haulers’ or ‘Long Covid’ are terms coined to describe those still struggling to recover from Covid-19 symptoms months after being infected. In July 2020 Chinese researchers launched one of the first studies of survivors in Wuhan, China.

Surveying 538 people who had recovered after being hospitalised, the Chinese researchers found survivors still suffered from respiratory, cardiovascular, and neurological effects caused by the virus more than three months later.

Subsequently, lingering symptoms have also been seen in those who were never hospitalised but had only mild or moderate illnesses. A September 2020 telephone survey of 292 adults recovering from Covid-19 conducted by the US CDC (Centers for Disease Control) revealed that 35% had not returned to their usual state of health two or more weeks after having a positive test.

The researchers noted that in contrast 90% of non-hospitalised influenza patients usually had recovered two weeks after their illness. Studies of Covid-19 survivors in France and Italy have echoed these findings.

A team of healthcare professionals in the UK estimated that 10% of those who contract Covid-19 will suffer prolonged symptoms. To make matters murkier, many Long Haulers either never had their illnesses confirmed by a lab test or tested negative at the time of their illness. False negatives may occur with diagnostic tests used to detect Covid-19.

A constellation of symptoms
Symptoms typically reported by Long Haulers include persistent cough, shortness of breath, chest pain, and fatigue. There is also a constellation of other reported symptoms. We’ll consider each of these in turn.

Respiratory: Some Long Haulers have evidence of damage to their lungs on radiographs, such as thickening of the spaces between lung tissue and scarring. Some have diminished lung capacity in pulmonary function tests. This is similar to another notorious coronavirus, Sudden Acute Respiratory Syndrome (SARSCoV- 1), which also still impaired the lungs of recovered patients two years after infection.

An article published in the on-line journal Eurosurveillance in September 2020 described diminished aerobic capacity while running in 199 Swiss Army recruits who recovered from Covid-19 and underwent a fitness test 45 days after their diagnosis.

Cardiac: Some severely ill Covid-19 patients have inflammation of the heart muscle (myocarditis), evidence of heart injury (based on elevated levels of troponin, a group of proteins involved in the contraction of heart and skeletal muscle), erratic heart rhythms, and thromboembolic diseases (forming blood clots that travel to the lungs, heart, or brain).

However, in a study of 26 Ohio State University athletes, all of whom had laboratory confirmed Covid-19 but either mild or no symptoms of illness, 46% showed silent evidence of myocarditis or prior myocardial damage on cardiac magnetic resonance imagery studies.

The researchers noted that myocarditis is a risk factor for sudden death in competitive athletes.

Neurocognitive: Common nervous system symptoms reported by Long Haulers include headaches, vertigo, impaired memory, inability to concentrate (often described as ‘brain fog’), and long-term loss of taste or smell.

A case report in the British Medical Journal also described sudden irreversible hearing loss in a 45-year-old man after being hospitalised from Covid-19. SARS-CoV-2 – the virus causing Covid-19 – is known to be able to penetrate brain tissue through the bloodstream and also may directly invade the olfactory nerve (impairing the sense of smell).

Other viral pathogens such as SARS-CoV-1, Middle East Respiratory Syndrome (SARS), and influenza have also been known to affect the cognitive abilities of recovering patients.

Systemic: Long Haulers often report fatigue and joint or muscle pain, mimicking what is seen in Chronic Fatigue Syndrome, a multi-systemic illness of unknown origin. In the Chinese study some recovered patients (mostly female) also developed hair loss (alopecia).

What’s the culprit?
Multiple theories abound for what is causing the symptoms seen in Long Haulers. Some theorise it is due to the SARS-CoV-2 virus invading and damaging multiple tissues of the body.

Others think the damage is caused by inflammation from the body’s immune system mounting an overly exuberant response to cast out the virus. Still others believe that damage to the body’s autonomic nervous system (which regulates a variety of systems, including heart rate, respiration, and digestion) could be responsible.

Faced with uncertain futures, sparse information, and occasional scepticism by the medical community, some Covid-19 survivors have formed on-line support groups for information sharing and advocacy.

The fact that prolonged illness after recovery occurs even in people with mild to moderate illnesses, including young adults, is alarming. The full and final statistics on Long Covid are yet to be written and further evidence of a chronic form of the disease is still unfolding.

This drives home the importance of measures to prevent contracting Covid-19 in the first place, such as wearing masks, practicing social distancing, mass testing and tracing and frequent handwashing. However, this level of vigilance is growing increasingly difficult to sustain in certain countries where people do not have sufficient civic awareness, do not respect authority, or heed the scientific evidence and advice being presented on a daily basis. Many people are also suffering from ‘Covid fatigue’ months into the pandemic, enduring repeated lockdowns and economic and social restrictions – or who have a skewed perception of their own risk. 

Deborah Carr, DVM, MPH, ACVPM currently works as a contractor for the US Department of Defense. Her areas of interest include zoonotic diseases, public health and biosurveillance.