Proteins such as transmembrane serine protease 2 (TMPRSS2), endoprotease (Furin) and cathepsin L (CTSL) activate the S protein of SARS-CoV-2 to facilitate the fusion of SARS-CoV-2 and IECs membranes, thereby enhancing virus infection and leading to GI symptoms (D’Amico et al., 2020; Hoffmann et al., 2020; Lu et al., 2020; Wang M. Y. et al., 2020; Zhong et al., 2020). This evidence concerns the gene CTSL and viral infectious disease.