In addition to the membrane-bound ACE2 serving as a potential therapeutic target for infectious disease [22,23,24], ACE2 is also a diagnostic and prognostic biomarker in other diseases, including pancreatic cancer [25], breast cancer [26], gallbladder cancer [27], non-small cell lung cancer [28], renal cell carcinoma [29], and hepatocellular carcinoma [30]. Here, ACE2 is linked to infectious disease.