ACE2 and pneumonia: Spikes of CoV-2 show 10–20 times higher binding affinity with ACE-2 relative to other CoVs (Wrapp et al., 2020), and thus, ACE-2-enriched heart, lung, bronchus, nasal mucosa, kidney, ileum, stomach, and other internal organs become the primary site of CoV-2 attack leading to respiratory sickness and pneumonia (Li X. et al., 2020).