ACE2 and COVID-19: Accordingly, our objectives were to review and perform a meta-analysis of the frequencies of AKI and RRT in critically ill COVID-19 patients and compare those frequencies with critically ill patients who were infected by respiratory viral infections due to viruses that bind or downregulate ACE2 (ACE2-associated viruses) and viruses that do not involve ACE2 (non-ACE2-associated viruses).