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Contrary to what doctors suggest and what happens in other diseases such as the flu, the overreaction of the immune system would not be involved in most of the fatal forms of Covid-19. Death would instead be linked to damage to the immune system by the virus. A conclusion that will require a review of the treatments provided to patients.
For many doctors and scientists, the sudden worsening of COVID-19 is in many cases linked to an overreaction of the immune system which is taken away by releasing a excessive production of cytokines, these molecules secreted by cells such as lymphocytes and the macrophages to fight the virus. ” Evidence is mounting to show that a portion of patients with severe Covid-19 are prone to syndrome cytokine shock Wrote the researchers of theUniversity College London hospitals (United Kingdom) in the review The Lancet.
The trace of cytokine storm, also called ” storm hyperinflammatory ”, did not come out of nowhere. The overproduction of cytokines it is particularly known in severe forms of respiratory diseases. This was particularly emphasized to explain the dangers of SARS 2003 and Seas, two others coronavirus. He is also suspected of having been at work during the main influenza pandemics, for example influence Spanish who killed around 50 million people in 1918-1919.
Less than 5% of severe Covid-19 cases
Except here it is: this explanation would be a false lead to explain the mortality in the case of SARS-CoV-2, let’s say two new studies today. ” Less than 5% of patients with Covid-19, including the sickest individuals, have a hyperinflammatory and potentially fatal immune response known as cytokine storm syndrome “Say the authors of the first study published on November 13 in Advances in science involving 168 patients with Covid-19. These severe patients have even fewerinflammation compared to an average person with flu, adds the study that analyzed the case of 168 adults with Covid-19 and 25 adults with flu.
The severity Conversely, the disease is linked to a “deeply suppressed” immune response, especially in the elderly. “ The virus [du Sars-Cov-2] it is a kind of double penalty for the elderly, explains Sean Leng, professor of medicine and immunology at Johns Hopkins University. These have weaker immune systems to begin with, so it is easier for the virus to enter and grow there. And when the virus starts killing the remaining immune cells, their situation will get even worse. “.
The Sars-Cov-2 virus is a double danger for the elderly
Covid-19: not particularly high levels of cytokines
A second study published in Jama corroborates these findings. Its authors compared the levels of three essential cytokines in the blood of ICU patients with several distinct conditions (Covid-19, severe acute respiratory infection, bacterial septic shock, cardiac arrest or severe trauma). Among these five patient groups, the cytokine level was found to be significantly lower in patients with Covid-19 than in those with septic shock or severe acute respiratory infection, and similar to those who suffered trauma or cardiac arrest, ” conditions that are not known for cytokine storms », Note the authors.
Unnecessary anti-inflammatory treatments?
These results question the anticitokine treatments administered to patients with severe forms of Covid, such as tocilizumab or sarilumab, which have nevertheless been the subject of great interest. Most patients with Covid-19 are also not candidates for treatment corticosteroids such as dexamethasone, the researchers say. However, the latter proved effective to treat critically ill patients, with a 34% reduced mortality risk. ” Drive the therapies immunosuppressive for the only small subset of Covid-19 patients with an overactive immune response is the only way to know if these approaches are ultimately useful “, explique Philip Mudd, emergency physician at the Barnes Jewish Hospital in Saint-Louis and co-author of the study by Science Advance.
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