COVID-19, the illness attributable to coronavirus SARS-Cov-2, has contaminated over 4 million folks in 212 nations, of whom at the very least 272,000 have died. The continuing financial and social impression of the pandemic is staggering, however regardless of a each day flood of information on the illness, few laypeople know that paradoxically, COVID-19 principally kills by way of an overreaction of the immune system, whose perform is exactly to struggle infections.
In a brand new evaluation article — explicitly focused to non-specialists as effectively — in Frontiers in Public Well being, a workforce of specialists from Zunyi Medical College evaluation the epidemiology, illness pathway, signs, prognosis, and present therapy of extreme COVID-19. They stress the key function of a probably deadly overreaction of the immune system in the development of the illness.
They clarify step-by-step what is understood about how the virus infects the airways, multiplies inside cells, and in extreme circumstances causes the immune defenses to overshoot with a “cytokine storm.” This storm is an over-activation of white blood cells, which launch too-great quantities of cytokines — inflammation-stimulating molecules — into the blood.
“Just like what occurs after an infection with SARS and MERS, information present that sufferers with extreme COVID-19 could have a cytokine storm syndrome. The quickly elevated cytokines appeal to an extra of immune cells akin to lymphocytes and neutrophils, leading to an infiltration of these cells into lung tissue and thus trigger lung damage,” explains creator Professor Daishun Liu from Zunyi Medical College, China.
The cytokine storm in the end causes excessive fever, extreme leakiness of blood vessels, blood clotting inside the physique, extraordinarily low blood strain, lack of oxygen and extra acidity of the blood, and build-up of fluids in the lungs (“pleural effusion”).
White blood cells are misdirected to assault and inflame even wholesome tissue, resulting in failure of the lungs, coronary heart, liver, intestines, kidneys, and genitals (A number of Organ Dysfunction Syndrome, MODS). This will likely worsen and shutdown the lungs (Acute Respiratory Misery Syndrome, ARDS) as a result of the formation of a so-called hyaline membrane, composed of particles of proteins and useless cells, lining the lungs, which makes absorption of oxygen tough. Most deaths as a result of COVID-19 are due to this fact as a result of respiratory failure.
Liu et al. clarify how in the absence of a particular antiviral remedy for COVID-19, the objective of therapy should be to the struggle the signs, reducing the mortality price by way of intensive upkeep of organ perform, for instance a man-made liver blood purification system or renal alternative remedy to filtrate the blood by way of mechanical means.
Particularly vital are strategies to complement or exchange lung perform, for instance by way of non-invasive mechanical air flow by way of a masks, air flow by way of a tube into the windpipe (if potential with the refinement of Optimistic Finish Expiratory Strain, PEEP, the place the ventilator delivers additional strain at the finish of every breath of maintain the lung vesicles open all through), the administration of heated and humidified oxygen through a tube in the nostril (“transnasal high-flow oxygen”), or a heart-lung bypass.
The authors conclude by stressing the significance of stopping secondary infections: SARS-Cov-2 additionally invades the intestines, the place it causes irritation and leakiness of the intestine lining, permitting the opportunistic entry of different disease-causing microorganisms. They advocate that this ought to be prevented with dietary assist, for instance with probiotics — helpful micro organism that shield in opposition to the institution of dangerous ones — and vitamins and amino acids to enhance the immune defenses and performance of the gut.
“As a result of therapy for now depends on aggressive therapy of signs, preventative safety in opposition to secondary infections, akin to micro organism and fungi, is especially vital to assist organ perform, particularly in the coronary heart, kidneys, and liver, to attempt to keep away from additional deterioration of their situation,” concludes Liu.
Reference: “Extreme COVID-19: A Evaluate of Latest Progress with a Look Towards the Future” by Peng Xie, Wanyu Ma, Hongbo Tang and Daishun Liu, 13 Might 2020, Frontiers in Public Well being.