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COVID-19, the disease caused by the SARS-Cov-2 coronavirus, has infected more than 4 million people in 212 countries, of which at least 272,000 have died. The continuing economic and social impact of the pandemic is staggering, but despite a daily rush of news about the disease, few lay people know that, paradoxically, COVID-19 kills primarily through an overreaction of the immune system, whose function is precisely fight infections.
In a new review article, also explicitly aimed at non-specialists, in Frontiers in public health, a team of experts from Zunyi Medical University reviews the current epidemiology, disease path, symptoms, diagnosis and treatment of severe COVID-19. They highlight the key role of a potentially lethal overreaction of the immune system in disease progression.
They explain step by step what is known about how the virus infects the airways, multiplies within cells, and, in severe cases, overwhelms the immune defenses with a “cytokine storm.” This storm is an over-activation of white blood cells, which release too large amounts of cytokines, molecules that stimulate inflammation, into the blood.
“Similar to what happens after infection with SARS and MERS, the data shows that patients with severe COVID-19 may have cytokine storm syndrome. Rapidly increasing cytokines attract excess immune cells, such as lymphocytes. and neutrophils, resulting in an infiltration of these cells into the lung tissue and therefore causing lung damage, “explains the author, Professor Daishun Liu, from Zunyi Medical University, China.
The cytokine storm eventually causes high fever, excessive leakage of blood vessels, clotting of blood within the body, extremely low blood pressure, lack of oxygen and excess acidity of the blood, and accumulation of fluids in the lungs (“stroke”). pleural “).
White blood cells are misdirected to attack and inflame even healthy tissue, leading to failure of the lungs, heart, liver, intestines, kidneys, and genitalia (Multiple Organ Dysfunction Syndrome, MODS). This can worsen and turn off the lungs (Acute respiratory distress syndrome, ARDS) due to the formation of the so-called hyaline membrane, made up of protein debris and dead cells, that line the lungs, making it difficult for oxygen to be absorbed. Most COVID-19 deaths are due to respiratory failure.
Liu et al. Explain how, in the absence of a specific antiviral cure for COVID-19, the goal of treatment should be to combat symptoms, reduce the mortality rate by intensively maintaining organ function, for example, an artificial system of purification of the liver blood or renal replacement therapy filter the blood by mechanical means.
Methods to supplement or replace lung function are especially important, for example, through non-invasive mechanical ventilation through a mask, ventilation through a tube into the trachea (if possible with refinement of final expiratory pressure). positive, PEEP, where the ventilator supplies additional pressure) at the end of each breath to keep the lung vesicles open), the delivery of heated and humidified oxygen through a tube to the nose (“high-flow transnasal oxygen”), or a heart-lung bypass.
The authors conclude by highlighting the importance of preventing secondary infections: SARS-Cov-2 also invades the intestines, where it causes inflammation and leaks in the intestinal lining, allowing opportunistic entry of other disease-causing microorganisms. They advocate that this is prevented with nutritional support, for example with probiotics (beneficial bacteria that protect against the establishment of harmful ones) and nutrients and amino acids to improve immune defenses and bowel function.
Because treatment for now is based on aggressive treatment of symptoms, preventive protection against secondary infections, such as bacteria and fungi, is particularly important in supporting organ function, especially in the heart, kidneys, and the liver, to try to prevent further deterioration of its symptoms. condition, “concludes Liu.
