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A hyperinflammatory phenomenon, “cytokine storms” appear to play a key role in severe cases of Covid-19. For the time being, they leave medicine relatively destitute.
Fever, fatigue, dry cough: four times out of five, Covid-19 causes “mild or moderate” symptoms. But, often, there is also breathing difficulty which can lead to severe acute respiratory syndrome. This is the case for about one in five or six people who require hospitalization to cope, according to the World Health Organization (WHO).
Difficulty breathing, feeling like your lungs are in a vice, lips or faces that are starting to turn blue are warning signs that should lead to an urgent consultation, according to the American health organization CDC.
The aggravation of the 7th day
A majority of hospitalized patients have severe pneumonia with bilateral involvement, which is the hallmark of the severe form of the disease, according to the WHO.
Often the aggravation comes suddenly, about seven days after the onset of the first symptoms, according to Professor Yazdan Yazdanpanah, head of the infectious diseases department of Bichat hospital in Paris.
This calendar retains a large part of mystery and variability, but regularly leads to an acute respiratory distress syndrome (ARDS). This situation where the lungs do not supply enough oxygen to the vital organs requires artificial ventilation with the use of a respirator.
“Cytokine shock”
“Evidence is accumulating to suggest that some of the patients suffering from severe forms of Covid-19 are subject to cytokinic shock syndrome”, writes, with British colleagues, Jessica Manson, specialist in inflammatory phenomena at University College Hospital in London, in the medical journal The Lancet.
This phenomenon of “hyperinflammatory storm” has been identified and described for only twenty years. He was singled out to explain the danger of two other respiratory diseases caused by coronaviruses, SARS (774 deaths, mainly in Asia, in 2002-2003) and Mers (Middle East respiratory syndrome, 866 deaths since 2012 ).
He is also suspected of having been at work during major influenza pandemics, such as the terrible “Spanish flu”, which killed around 50 million people between 1918 and 1919.
“Exuberant immune response”
Cytokines are substances naturally produced by cells of the immune system to regulate the immune action, in particular to favor the inflammatory reaction which is a natural defense response of an attacked organism. However, in the case of the “cytokine storm”, there is a runaway of this system which leads to a hyperinflammatory reaction which can become lethal.
How important are these storms in the lethal gears of severe Covid-19 cases? “This is a very good question,” replies the American specialist in microbiology and immunology, Stanley Perlman, who has studied these phenomena in the cases of Sras and Mers.
“I think an exuberant immune response is what really kills patients (from Covid-19) by destroying the tissue. But that’s not a certainty, ”said the University of Iowa expert.
How to calm the storm?
It should be possible to calm the storm in the lungs without lowering the immune barriers of patients. For now, medicine is groping and mounting emergency trials as the pandemic progresses.
For example, in Paris, the public hospital group AP-HP has launched, in recent days, the Corimmuno trial to test several drugs against these excessive inflammatory reactions.
“At the present time,” there is “no” effective and proven therapeutic approach against this phenomenon, deplores Professor Perlman. The academic stresses that administering corticosteroids, common anti-inflammatory drugs, would “definitely be harmful” for patients with Covid-19.
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