Infection causes production of many inflammatory factors, like interleukin-1 (IL-1), interferon-gamma (IFN-gamma), tumor necrosis factor (TNF), etc down-regulate the expression of ACE2.36 This down-regulation activates the renin-angiotensin system (RAS) and damage to the heart, lungs, intestines, and other organs. Here, ACE2 is linked to infection.