AOC3 and viral infectious disease: In severe COVID-19 patients, the plasma levels intercellular adhesion molecule 1 (I-CAM-1), vascular cell adhesion molecule-1 (VCAM-1), and vascular adhesion protein-1 (VAP-1), are elevated (Escher et al., 2020; Tong et al., 2020), indicating that the endothelial barrier is damaged consecutive to viral infection.