How COVID-19 kills: New study explains the mechanisms of the new coronavirus

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COVID-19The disease caused by the SARS-Cov-2 coronavirus has infected over 4 million people in 212 countries, of which at least 272,000 have died. The ongoing economic and social impact of the pandemic is astonishing, but despite a daily flood of news about the disease, few lay people know that, paradoxically, COVID-19 is mainly killed by an overreaction in the immune system, the function of which is to fight infection.

In a new review article – which is also aimed specifically at non-specialists – in Limits to public health, a team of experts from Zunyi Medical University, is studying the epidemiology, course of the disease, symptoms, diagnosis, and current treatment for severe COVID-19. They emphasize the key role of a potentially fatal immune system overreaction as the disease progresses.

They explain step by step what is known about how the virus infects the respiratory tract, multiplies in cells and, in severe cases, causes the immune system to overflow with a “cytokine storm”. This storm is an over-activation of the white blood cells, which release excessive amounts of cytokines – inflammation-stimulating molecules – into the blood.

“Similar to SARS and MERS infection, data shows that patients with severe COVID-19 may have cytokine storm syndrome. The rapidly increased cytokines attract an excess of immune cells such as lymphocytes and neutrophils, which leads to infiltration of these cells into the lung tissue and thus causes lung injuries, ”explains the author Professor Daishun Liu from Zunyi Medical University, China.

Ultimately, the cytokine storm causes high fever, excessive blood vessel leakage, blood clotting in the body, extremely low blood pressure, lack of oxygen and excessive acidity in the blood, as well as fluid accumulation in the lungs (“pleural effusion”). .

White blood cells are misdirected to attack and inflame even healthy tissue, leading to failure of the lungs, heart, liver, intestine, kidneys and genitals (Multiple Organ Dysfunction Syndrome, MODS). This can worsen and switch off the lungs (Acutes Respiratory Distress Syndrome, ARDS), since a so-called hyaline membrane is formed, which consists of protein debris and dead cells and lines the lungs, making it difficult for oxygen to be absorbed. Most COVID-19 deaths are therefore due to respiratory failure.

Liu et al. Explain how, in the absence of a specific antiviral cure for COVID-19, the goal of the treatment must be to fight the symptoms and reduce the mortality rate through intensive maintenance of organ function, for example through an artificial liver blood purification system or kidney replacement therapy to reduce the blood by mechanical means to filter.

Methods for supplementing or replacing lung function are particularly important, for example, through non-invasive mechanical ventilation through a mask, ventilation through a tube into the trachea (if possible, with the refinement of positive end-expiratory pressure (PEEP), at which the ventilator delivers additional pressure keep the alveoli open at the end of each breath), the administration of heated and humidified oxygen through a tube in the nose (“transnasal oxygen with high flow rate”) or a cardiopulmonary bypass.

In conclusion, the authors emphasize the importance of preventing secondary infections: SARS-Cov-2 also penetrates the intestine, where it causes inflammation and leaks in the intestinal mucosa and enables the opportunistic entry of other disease-causing microorganisms. They advocate that this should be prevented with nutritional support, for example with probiotics – useful bacteria that protect against the formation of harmful bacteria – and nutrients and <span data-cmtooltip = "

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“Since the treatment is currently based on an aggressive treatment of the symptoms, preventive protection against secondary infections such as bacteria and fungi is particularly important in order to support organ function, particularly in the heart, kidneys and liver, and to prevent further worsening of the symptoms.” , concludes Liu.

Reference: “Heavy COVID-19: A Look Back at Recent Advances Looking to the Future” by Peng Xie, Wanyu Ma, Hongbo Tang and Daishun Liu, May 13, 2020, Limits to public health.
DOI: 10.3389 / fpubh.2020.00189

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