Table 1.

MERS-CoV, SARS-CoV, and SARS-CoV-2 characteristics.

	MERS-CoV	SARS-CoV	SARS-CoV-2
Host cell entry receptor	DPP4	ACE2	ACE2
Shared genome with SARS-CoV-2 [12]	50%	79%	N/A
Reservoir [52]	Bats	Bats	Bats
Risk factors for poor outcomes	Advanced age, male sex, DM, HTN, cancer, lung disease [12]	Advanced age, male sex [55]	DM, HTN, advanced age, cardiovascular disease, cancer [13,14]
	Cytokine storm,		Cytokine storm,
	C5a-induced CD8+ T cell reduction [53,54]	Cytokine storm, reduction in CD8+ T cells	reduced CD4+/CD8+ T cell ratio [56]
Severity of disease etiology

ACE2, angiotensin-converting enzyme 2; C5a, complement component 5a; DM, diabetes mellitus; DPP4, dipeptidyl peptidase-4; HTN, hypertension; N/A, not applicable.