A study from Northwestern University, Evanston, Illinois, found that nearly half of Covid patients developed secondary ventilator-associated bacterial pneumonia, which became a "major cause of death" in Covid patients. Bacterial infections can even exceed the death rate from the viral infection itself. Those who were cured of their secondary pneumonia were likely to live. The data suggested that mortality from the virus itself was relatively low. The researchers also found evidence that Covid does not cause a "cytokine storm" - an overwhelming inflammation leading to organ failure - which was often thought to be the cause of death.