(CN) — Covid-19, which has infected over 4 million people worldwide and killed nearly 300,000, triggers a lethal immune response researchers say is critical to understand and treat to reduce deaths from the pandemic.
In an article published Wednesday in Frontiers in Public Health, experts from the Department of Respiratory and Critical Medicine at Zunyi Medical University in China explained step-by-step how Covid-19, caused by coronavirus SARS-Cov-2, causes an overactive immune response to fight off the disease. This response, the researchers say, is responsible for the most severe cases and deaths.
The study includes preliminary results from treatment options that have been employed to treat Covid-19 patients in China with specific patient monitoring data health care professionals should review when treating coronavirus patients.
In the absence of an antiviral cure, researchers posture the goal of coronavirus treatment must be to fight the symptoms that cause an overactive immune response and lower the mortality rate through intensive maintenance of organ function.
Plasma from recovered patients can also be used to treat patients with severe Covid-19, as using plasma to treat sudden acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) was found to be an effective treatment that significantly reduced the mortality rate of the diseases, according to the study.
The third acute infectious disease caused by coronavirus — viruses which transfer from animals to humans — in the 21st century, Covid-19 causes an immune response similar to that seen in patients infected with SARS and MERS.
Covid-19 enters the airways through respiratory droplets and close contact with people who have the disease — including those who are asymptomatic. It multiples inside cells causing toxicity and triggering excessive immune responses.
The systemic inflammation causes what is called a cytokine storm, resulting in lung injury and causing patients with severe disease to develop respiratory failure and die. The over-activation of white blood cells releases too-great amounts of cytokines — inflammation-stimulating molecules — into the blood.
"Similar to what happens after infection with SARS and MERS, data show that patients with severe COVID-19 may have a cytokine storm syndrome. The rapidly increased cytokines attract an excess of immune cells such as lymphocytes and neutrophils, resulting in an infiltration of these cells into lung tissue and thus cause lung injury,” Professor Daishun Liu of Zunyi Medical University said in a statement.
The cytokine storm immune response causes high fever, excessive leakiness of blood vessels, blood clotting, extremely low blood pressure, lack of oxygen and excess acidity of the blood, in addition to fluid build-up in the lungs, according to the study.
When the white blood cells attack and injure healthy tissue when trying to eliminate Covid-19, patients experience multiple organ failure of their lungs, heart, liver, intestines, kidneys and genitals.
The organ failure can lead to the shutdown of the lungs — Acute Respiratory Distress Syndrome — due to the formation of the hyaline membrane, a build-up of proteins and dead cells lining the lungs which makes oxygen absorption difficult, according to the study.
Most deaths from Covid-19 are thus due to respiratory failure.
But the mortality rate can be controlled by maintaining organ function through using an artificial liver blood purification system or renal replacement therapy to filtrate the blood through mechanical means.
Continuous renal replacement therapy and artificial liver support used to support Covid-19 patients in China shortened the length of Intensive Care Unit stays, according to the study.
Methods to supplement or replace lung function include non-invasive medical ventilation through a mask, ventilation through a tube into the windpipe, administration of heated and humidified oxygen via a tube in the nose, or a heart-lung bypass.
The researchers also stress the importance of preventing secondary infections where Covid-19 invades the intestines, causing inflammation and leakiness of the gut lining, which creates an opportunity for other disease-causing microorganisms to enter the body and can even exacerbate lung injury.
Digestive tract infections could be prevented with nutritional support via probiotics — beneficial bacteria which can protect against harmful ones — and nutrients and amino acids, which improve immune defenses and intestine function.
“Because treatment for now relies on aggressive treatment of symptoms, preventative protection against secondary infections, such as bacteria and fungi, is particularly important to support organ function, especially in the heart, kidneys, and liver, to try and avoid further deterioration of their condition," Liu said.
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