Unlike regular pneumonia, pneumonia caused by the coronavirus disease 2019 (Covid-19) spreads like many “wildfires” throughout the lungs, researchers said.

This may explain why Covid-19 pneumonia lasts longer and causes more harm than typical pneumonia, according to the researchers at Northwestern Medicine in Chicago.

The research team said that their aim is to make Covid-19 more like a bad cold.

For the study, the team analyzed immune cells from the lungs of Covid-19 pneumonia patients and compared them to cells from patients with pneumonia caused by other viruses or bacteria.

While other types of pneumonia rapidly infect large regions of the lungs, Covid-19 begins in numerous small areas of the lungs. It then uses the lungs’ own immune cells to spread across the lungs over many days or even weeks.

This is similar to how multiple wildfires spread through a forest, the study authors explained.

As Covid-19 pneumonia slowly moves through the lungs, it leaves damaged lung tissue in its wake and contributes to the fever, low blood pressure and organ damage common in Covid-19 patients, the team said.

The long duration of Covid-19 pneumonia, rather than greater severity, may be why it causes more serious complications than other types of pneumonia, according to the study authors.

The report was published this week in the journal Nature.

The researchers also identified immune cells – macrophages and T cells – that could be important targets when treating severe Covid-19 pneumonia.

Macrophages typically protect the lungs, but can be infected by the new coronavirus and help spread the infection through the lungs, the team noted in a Northwestern news release.

In a clinical trial early this year, the investigators plan to test an experimental drug that targets these immune cells in Covid-19 pneumonia patients. The drug reduces the inflammatory response of these immune cells.

“Our goal is to make Covid-19 mild instead of severe, making it comparable to a bad cold,” study co-author Dr. Scott Budinger said in the news release. He is chief of pulmonary and critical care medicine at Northwestern University Feinberg School of Medicine.

Study co-author Dr. Richard Wunderink, professor of pulmonary and critical care medicine at Feinberg and medical director of Northwestern Medicine’s ICU, added that “this effort truly represents a ‘moonshot’ in COVID-19 research.” CURRENTPH