The SARS-CoV-2 virus binds to a specific receptor (ACE2) that is expressed in a multitude of different cells in our bodies, most curiously the endothelial cells that line up your vessels. Some hypothesis suggest that the disruption of the systems associated with ACE2 is what causes downstream effects that lead to symptoms of COVID. By virtue of infecting blood vessels, the virus can cause them to stop functioning properly, and thus impair the supply of oxygen to otherwise healthy tissue. These hypoxic microlesions, which have been found even in the brain of patient populations, could in turn be responsible for some of the sequelae that the infection leaves behind after the end of acute period of the disease.

The extent to which damage is caused, and the extent to which the body can recover will evidently dictate the period of convalescence. Because symptoms vary wildly from case to case, pinpointing general routes of treatment or estimating the duration of recovery is a highly complex problem.