The turning point for people with COVID-19 typically comes in the second week of symptoms.
As most people begin to recover, a few others find it increasingly difficult to breathe and wind up in the hospital.
It has been theorized that those whose lungs begin to fail are victims of their own overactive immune systems.
In a new study, researchers found that an out-of-control immune response is not the main problem for the vast majority of hospitalized COVID-19 patients.
Only 4% of patients in the study had the sky-high levels of immune molecules that signify a so-called “cytokine storm.”
The rest had inflammation, but not a remarkably high amount for people fighting infection. If anything, the COVID-19 patients had less inflammation than a comparable group of influenza patients.
The findings help explain why anti-inflammatory medications such as dexamethasone benefit only a fraction of people with severe COVID-19, and suggest that more research is needed to identify the causes of respiratory failure in COVID-19 patients.
The research was conducted by a team from Washington University School of Medicine in St. Louis and elsewhere.
In the study, the team analyzed immune cells and molecules in blood samples from 168 COVID-19 patients, 26 influenza patients, and 16 healthy people.
They found that cytokine storm does happen in COVID-19, but it’s relatively rare, even in the COVID-19 patients that go on to have respiratory failure and require a ventilator.
The majority of the COVID-19 patients with acute respiratory failure not only did not have a cytokine storm, they had less inflammation than influenza patients who were equally ill.
But now this idea has gotten established that respiratory failure in COVID-19 is driven by cytokine storm, and lots of unproven anti-inflammatory treatments are being given to critically ill COVID-19 patients in an attempt to suppress the cytokine storm.
That worries the researchers because such treatments are unlikely to help most people with COVID-19.
The team says the key will be to find a way to identify the people at high risk for a cytokine storm when they first arrive at the hospital so that steroid treatment can be appropriately targeted to the ones most likely to benefit and least likely to be harmed.
With cytokine storm largely ruled out, the cause of most cases of respiratory failure in COVID-19 patients remains unknown.
One author of the study is Philip Mudd, MD, Ph.D.
The study is published in Science Advances.
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