TABLE 1.

Comparison of SARS-CoV-1, MERS, and SARS-CoV-2.

	SARS-CoV-1	MERS	SARS-CoV-2
First emergence	November, 2002	April, 2012	December, 2019
Regions affected
Emerged	China	Jordan	China
Spread to	China, Vietnam, Hong Kong, Singapore, Taiwan, Canada	Saudi Arabia, Jordan, Yemen. Few cases in United States	Worldwide pandemic
Natural host	Bats	Bats	?Bats, ?pangolins
Intermediate animal host	Palm civet, ?bats	Camel, ?bats	?Bats, ?pangolins (controversial)
Common symptoms	Fever, tiredness, dry cough, myalgia, nasal congestion, sore throat, diarrhea, lymphopenia	Cough, shortness of breath, headache, sore throat, fever, loss of appetite, diarrhea, nausea, and vomiting	Fever, shortness of breath, sore throat, cough, tiredness, anosmia, dysgeusia, diarrhea. Leukocytosis (?pregnancy related) (Magee et al., 2021)
Genomic structure	Single-stranded RNA (ssRNA)	Single-stranded RNA (ssRNA) (Kim et al., 2015)	Positive single-stranded RNA virus
	20% less ACE2- binding affinity than SARS-CoV-2 (Zhu et al., 2020)		Shares 80% sequence identity with SARS- CoV-1 and 50% similarity with MERS (Naqvi et al., 2020)
Variants of concern	TOR2, Urbani,	MH013216,	Alpha, Beta,
	CUHK-W1, CUHK-	MN120513,	Gamma,
	Su10, HKU-39849,	MN120514,	Delta, Epsilon, Eta,
	SIN2500, SIN2677,	MH306207,	Iota, Kappa, 1.617.3,
	SIN2679, SIN2748,	MH359139,	Mu, Zeta
	SIN2774, TW1, BJ01,	MH371127,	Omicron
	BJ02, BJ03, BJ04, GZ01	MH432120, MH454272
Cases	8,098 reported cases	2,578 confirmed cases	397 million cases to date
Reinfection	No reported cases	No reported cases	+++
Case fatality rate	9.6%	34.3%	4.4%