What is post-COVD-19 syndrome or long COVID?

Even after a primary COVID-19 infection clears out, some people may show symptoms weeks or months later and they experience long COVID. 

The COVID-19 pandemic has put a massive strain on the healthcare system due to its mysterious and fast-spreading nature. Scientists and healthcare workers are doing their best to understand and treat this disease. The immune system is in overdrive during a coronavirus infection in order to clear out the excessive viral load. Treating a COVID-19 infection involves using antiviral agents and controlling the overactive immune system so as to prevent further damage such as multi-organ dysfunction syndrome.

Some people experience symptoms weeks and months even after the COVID-19 infection has cleared out. This is called post-COVD-19 syndrome or long COVID. The persistent infection can occur even if their first infection was mild or asymptomatic. According to the CDC, the most common symptoms of long COVID include tiredness or fatigue, brain fog, headache, loss of smell or taste, dizziness on standing, heart palpitations, chest pain, difficulty breathing, cough, joint or muscle pain, anxiety, fever etc. 

Tony R Reid and colleagues extensively discussed the possible roots of the post-COVID-19 syndrome and its management in a review that was published in Clinical Reviews in Allergy and Immunology. They described how the overactive immune system caused post-infection issues. They state that the post-COVID-19 syndrome could be a “hidden public health disaster”. These issues are ignored or dismissed but can put huge stress on the healthcare system if not addressed. Currently, the primary focus is to abate the complicated and severe primary COVID-19 infections and to curtail their spread. It leaves almost no room for considering the post-infection scenarios. 

The SARS-CoV-2 virus, when uncontrolled, triggers a systemic inflammatory response syndrome (SIRS). The host immune system counter-attacks SIRS through a compensatory inflammatory response syndrome (CARS). The balance between SIRS and CARS is extremely crucial and if the scale dips too much in either one of the directions, it can have dangerous consequences. The immune system should return to normal after CARS and enable recovery. Extended CARS can lead to immunosuppression and cause post sepsis syndrome. Prolonged immunosuppression can also make the patient susceptible to COVID-19 relapse or another bacterial infection. 

Long COVID manifests itself in multiple ways and it varies from one person to another. It can appear as pulmonary fibrosis causing lack of oxygen supply, cardiac dysfunction like heart failure, neurological impairment like loss of smell or taste, and clotting complications. A research team from Max Planck Centre for Physics and Medicine and Friedrich Alexander University in Germany went on to understand the vascular changes observed in patients who have suffered and recovered from a COVID-19 infection. The study was published in Biophysical Journal

The team of scientists used a novel method called real-time deformability cytometry to understand the morphology of blood cells in COVID-19 recovered patients. In this method, the scientists passed the red blood cells and white blood cells through a narrow tube at high speed. The cells get stretched and a high-speed camera takes pictures of these cells through a microscope. This method can be helpful for many such future experiments as it is cost-effective and does not include the laborious work of radiolabelling. It can also analyse up to 1000 blood cells per second. 

The team observed that the surface conformation of the RBCs was different in the recovered patients even seven months after the COVID-19 infection cleared out. The slightly damaged RBCs caused impaired oxygen supply which could explain all the vascular problems seen during post-COVID-19 syndrome. The WBCs in these individuals were also observed to be softer which is a common occurrence in systemic infections. The team suspects that the virus was capable of causing damage to the cytoskeleton of the blood cells hence rendering long term damage. 

Managing post-COVID-19 syndrome is a tricky task due to a lack of awareness. It is also difficult to determine if the illnesses are a result of a COVID-19 infection or not. Management strategies for treating long COVID will vary depending on the level and type of damage seen in the patients. Developing immunomodulatory therapies can help to take care of the prolonged immunosuppressive behaviour seen post the infection.

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