What triggers severe COVID? Infected immune cells hold clues

Smiriti Malapaty in Nature:

Since the early days of the pandemic, research has suggested that inflammation leads to significant respiratory distress and other organ damage, hallmarks of severe COVID-19. But scientists have struggled to pinpoint what triggers the inflammation.

The latest studies implicate two types of white blood cells — macrophages in the lungs, and monocytes in the blood — which, once infected with the virus, trigger the inflammation. The studies also provide conclusive evidence that the virus can infect and replicate in immune cells — and reveal how it enters those cells. Evidence of such infections has been mixed until now.

The studies offer a plausible explanation for how severe COVID-19 progresses, says Malik Peiris, a virologist at the University of Hong Kong. “I don’t think it is the only or most important pathway, but it is certainly interesting.”

More here.