Ventilator-Associated Bacterial Pneumonia, Not Cytokine Storm, Found as Key Factor in COVID-19 Fatalities

Summary: A recent study found that secondary bacterial pneumonia, rather than the much-discussed “cytokine storm,” is a significant factor in COVID-19-related fatalities. Almost half of the patients who required mechanical ventilation support were affected by this secondary bacterial infection. By applying machine learning to analyze medical records, the researchers found that those who recovered from secondary pneumonia were more likely to survive, whereas unresolved cases increased mortality risk. 

The study, which challenges the cytokine storm theory, emphasizes the importance of preventing and aggressively treating secondary bacterial pneumonia in critically ill patients. 

Key Facts: 

Almost half of the patients with COVID-19 who required mechanical ventilation support developed secondary bacterial pneumonia, which contributed significantly to fatalities. 

Patients who recovered from secondary bacterial pneumonia had a higher chance of survival, while those with unresolved cases were more likely to die. 

The study challenges the widely-held belief that a “cytokine storm” causes death in COVID-19 patients, emphasizing the importance of prevention and aggressive treatment of secondary bacterial pneumonia in critically ill patients. 

Source: Northwestern University 

Secondary bacterial infection of the lung (pneumonia) was extremely common in patients with COVID-19, affecting almost half the patients who required support from mechanical ventilation. 

By applying machine learning to medical record data, scientists at Northwestern University Feinberg School of Medicine found that secondary bacterial pneumonia that does not resolve was a key driver of death in patients with COVID-19. It may even exceed death rates from the viral infection itself. 

The scientists also found evidence that COVID-19 does not cause a “cytokine storm,” so often believed to cause death. 

The study was recently published in the Journal of Clinical Investigation. 

“Our study highlights the importance of preventing, looking for and aggressively treating secondary bacterial pneumonia in critically ill patients with severe pneumonia, including those with COVID-19,” said senior author Dr. Benjamin Singer, an associate professor of medicine at Northwestern University Feinberg School of Medicine and a Northwestern Medicine pulmonary and critical care physician. 

The investigators found nearly half of patients with COVID-19 develop a secondary ventilator-associated bacterial pneumonia. “Those who were cured of their secondary pneumonia were likely to live, while those whose pneumonia did not resolve were more likely to die,” Singer said. 

“Our data suggested that the mortality related to the virus itself is relatively low, but other things that happen during the ICU stay, like secondary bacterial pneumonia, offset that.” 

The study findings also negate the cytokine storm theory, said Singer, also the Lawrence Hicks Professor of Pulmonary Medicine at Feinberg. “The term ‘cytokine storm’ means an overwhelming inflammation that drives organ failure in your lungs, your kidneys, your brain and other organs,” Singer said. 

“If that were true, if cytokine storm were underlying the long length of stay we see in patients with COVID-19, we would expect to see frequent transitions to states that are characterized by multi-organ failure. That’s not what we saw.” 

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