ACE2 and viral infectious disease: Importantly, the team also proposed the theory of “malignant circulation” for SARS-CoV-2 invasion of the kidney; that is, in the early stage of SARS-CoV-2 invasion of the kidney, it mainly binds ACE2 (the expression level is higher than that of KIM1 in the physiological state), and after virus-induced acute kidney injury, the expression level of KIM1 is upregulated, thus promoting secondary viral infection mediated by KIM1 and ACE2, aggravating kidney injury and further upregulating KIM1.