CHICAGO, Jan. 12 (Xinhua) -- A study of Northwestern Medicine shows that the severe complications of COVID-19 compared with other pneumonias might be related to the long course of disease rather than more severe disease.

Instead of rapidly infecting large regions of the lung within hours, like bacteria or viruses like influenza do, the virus causing COVID-19 sets up shop in multiple small areas of the lung, hijacks the lungs' own immune cells and uses them to spread across the lung over a period of many days or even weeks.

As the infection slowly moves across the lung, it leaves damage in its wake and continuously fuels the fever, low blood pressure and damage to the kidneys, brain, heart and other organs in patients with COVID-19.

As a result of the detailed analysis, the researchers identified critical targets to treat severe SARS-CoV-2 pneumonia and lessen its damage. The targets are the immune cells: macrophages and T cells. The study suggests macrophages, cells typically charged with protecting the lung, can be infected by SARS-CoV-2 and can contribute to spreading the infection through the lung.

The study also found that the mortality among patients on a ventilator for COVID-19 was lower than patients on a ventilator due to regular pneumonia.

"Our goal is to make COVID-19 mild instead of severe, making it comparable to a bad cold," said study co-senior author Scott Budinger, chief of pulmonary and critical care medicine at Northwestern University Feinberg School of Medicine and Northwestern Medicine.

COVID-19, like influenza, is unlikely to ever go away, even if much of the population is vaccinated, said senior co-author Ben Singer, assistant professor of pulmonary and critical care medicine at Feinberg and a Northwestern Medicine physician.

This is the first study in which the researcher analyzed immune cells from the lungs of COVID-19 pneumonia patients in a systematic manner and compared them to cells from patients with pneumonia from other viruses or bacteria.

The study was published in Nature on Monday.

Northwestern Medicine is the collaboration between Northwestern Memorial HealthCare and Northwestern University Feinberg School of Medicine, which includes research, teaching and patient care.