The coronavirus pandemic is in its third year with no sign of abatement. In its wake, long COVID has emerged as an increasingly worrisome global health concern as it could be debilitating in many people who get COVID-19. The condition affects people old and young, vaccinated or unvaccinated, and after asymptomatic, mild, or severe COVID-19. It is more common in women than in men, with a peak incidence in middle-aged people.
The World Health Organization defines Long COVID as a condition that occurs longer than three months after the acute illness in someone who had COVID, with symptoms -- lasting two months or more -- that cannot be explained by another diagnosis.
Long COVID is a syndrome with protean manifestations; more than 200 symptoms have been associated with the disorder ranging from respiratory, cardiac, neurological, and gastrointestinal, to systemic, causing symptoms like headache, mood disturbance, chronic fatigue, brain fog, cognitive dysfunction, chest pain, shortness of breath, gastrointestinal distress, nausea, vomiting, post-exertional malaise, and joint pain. These symptoms typically wax and wane.
An estimated 10% to 30% of COVID-19 patients develop some degree of protracted, drawn-out symptoms. After getting two doses of a COVID-19 vaccine, adults infected are 40% less likely to develop long-term symptoms. The study also found that unvaccinated COVID-19 patients can be partially protected from long COVID if they receive post-COVID vaccination compared to those who remain unvaccinated.
Long COVID is likely an umbrella term for related but distinct category of symptoms having different underlying causes in different patients. Some long COVID patients have an overactive immune or inflammatory response that could not be tamped down, attacking the body in the process resembling an autoimmune disease. It may be related to viral remnants lingering after recovering from the initial acute infection. Long-term infection is another possibility with the virus holing up in hard-to-reach places in the body. According to another just-published study, a reservoir of viral remnants is the gastrointestinal tract with prolonged shedding of SARS-CoV-2 RNA fragments in the feces well after the virus has been cleared from the respiratory system. Another study identifies factors that predict increased risk of long COVID: high levels of viral RNA early during an acute infection, the presence of certain autoantibodies, the reactivation of Epstein-Barr virus and having Type 2 diabetes.
- In the circulatory system, microscopic blood clots may persist blocking blood flow in the capillaries and limiting oxygen delivery to muscles and other body tissues causing severe fatigue despite having apparent normal hearts and lungs. Small fiber neuropathy associated with autonomic nervous system dysfunction has been documented leading to commonly seen heart rate irregularity, breathing, and digestion problems.
- In the brain, even mild COVID cases can experience unremitting cognitive impairments. Over-activation of brain immune cells, the microglia, causes chronic brain inflammation. The amount of blood flow reaching the brain is reduced as well and localized neuronal cell loss has been documented in various loci of the brain.
- In the lungs, shortness of breath is a common symptom in long COVID patients despite having normal chest X-ray, CT scan, and functional test. Specialized MRI scan has demonstrated subtle lung damage. Plausible causes include poor oxygen uptake from thickened barrier layer separating the alveoli and blood vessels.
Given the sheer size of the problem, many hospitals now offer post-Covid recovery programs which bring multidisciplinary teams of doctors to care for patients with multiorgan problems. Identifying the specific illnesses of each patient will be crucial for guiding treatment. Currently, few evidence-based treatments exist; treatment will be limited to managing symptoms and interventions like physical, occupational, and respiratory therapy. Ongoing research is giving us a better understanding of the condition, and more effective treatments will emerge. Lately, certain antiviral for Covid-19 has been reported to dramatically ameliorate long COVID symptoms.
