Study result: Cause of death in patients with Covid-19

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Although many risk factors such as gender, age, frailty, pregnancy, or obesity are now known, it is still not completely clear why some people develop a severe and some mild course of Covid-19.

Last year, a microscopic study from Germany supported the theory of a so-called cytokine storm: the immune system overshoots the mark and sometimes causes more damage with this exaggerated reaction than the virus itself.

A recent U.S. study analyzed the health data of 585 patients in the intensive care unit of Northwestern Memorial Hospital in Chicago: all were diagnosed with severe pneumonia and respiratory failure, and 190 were infected with the coronavirus. And came to a different conclusion.

The result: secondary bacterial infections of the lungs (pneumonia) were widespread in patients with Covid-19 and affected nearly half of the patients who required mechanical ventilation. If not resolved, secondary bacterial infection was a leading cause of death in patients with Covid-19. The researchers could find no evidence that Covid-19 causes a “cytokine storm” that leads to death.

The study was recently published in the Journal of Clinical Investigation. (You can read the study here).

Bacterial superinfection
The study authors said that bacterial superinfection of the lung as a risk factor in patients with covid-19 had been underestimated because most centers have not looked for it. “Our study underscores the importance of preventing, seeking out and aggressively treating secondary bacterial pneumonia in critically ill patients with severe pneumonia, including those with covid-19,” said pulmonary and critical care physician Benjamin Singer, lead author of the study and professor of medicine at Northwestern University Feinberg School of Medicine.

“Those who were cured of their secondary pneumonia had a high probability of survival, while those whose pneumonia did not resolve were more likely to die,” Singer said. “Our data suggest that mortality associated with the virus itself is relatively low, but that other factors that occur during the ICU stay, such as secondary bacterial pneumonia, offset this.”

The study’s findings refute the cytokine storm theory; Singer said, “The term ‘cytokine storm’ means overwhelming inflammation that leads to organ failure in the lungs, kidneys, brain and other organs. If the cytokine storm were the cause of the long retention time we see in patients with Covid-19, we would expect multiorgan failure to occur frequently. However, we have not seen that.”