Table 2. Coronaviruses in humans.

Coronavirus genus	Strains	Cellular receptors	References
Alpha coronavirus	HCoV-229E HCoV-NL63	Human aminopeptidase N (CD13) ACE2	(Pene et al., 2003) (Jones et al., 2013)
Beta coronavirus	HCoV-OC43 HCoV-HKU1 SARS-CoV MERS-CoV SARS-CoV-2	9-O-acetylated sialic acid 9-O-acetylated sialic acid ACE2 DPP4 ACE2	(Walsh et al., 2013) (Arbour et al., 2000) (Arbour et al., 1999) (Ramadan and Shaib, 2019) (Tu et al., 2020)