The initial range of COVID-19 symptoms is explained by expression of ACE2 and TMPRSS2 or CTSL/B in several types of epithelial cells in the nasal cavities, lung, gastrointestinal tract, and eye (Muus et al., 2021; Sungnak et al., 2020; Ziegler et al., 2020). Here, ACE2 is linked to COVID-19.