In the SARS-CoV infection, it has been shown that the infection mechanism can occur by endocytosis and the spike activation is processed by CatL (Figure 1) (Simmons et al., 2004; Simmons et al., 2005; Huang et al., 2006; Bosch et al., 2008; Ou et al., 2020). The gene discussed is CTSL; the disease is infection.