Table 1.

Epidemiological comparison of human coronaviruses.

Biological features	SARS-CoV-1	MERS-CoV	SARS-CoV-2
Classification	β -CoV (lineage B)	β-CoV (lineage C)	β-CoV (lineage B)
First outbreak	2002, Guangdong, China	2012, Saudi Arabia	2019, Wuhan, China
Countries affected	32	109	210
Estimated Ro value	2	<1	2.68
Virus spreader	Bats	Bats	Bats
Intermediate host	Palm civets, raccoons, and dogs	Camels	Pangolins and minks
Incubation period	4–7 days	2–15 days	4–14 days
Transmission	Respiratory droplets	Respiratory droplets	Respiratory droplets
Season	Winter	Winter	Winter
Receptors to host cells	hACE2	hACE2	hACE2
Signs and symptoms	Fever, headache, dry cough, dyspnea, diarrhea, and ARDS	Fever, chills, sore throat, dyspnea, diarrhea and vomiting, acute renal impairment, and ARDS	Fatigue, fever, dry cough, dyspnea, anosmia, tachypnea, and ARDS
Mortality (%)	9%	34.5%	3.6%
References	(24–27)	(4, 7, 9, 28–30)	(12, 15, 18, 23, 31, 32)

SARS-CoV-1, severe acute respiratory syndrome coronavirus; MERS-CoV, Middle East respiratory syndrome coronavirus; SARS-CoV-2, severe acute respiratory syndrome coronavirus type 2; hACE2, human angiotensin-converting enzyme 2; ARDS, acute respiratory distress syndrome.