COVID-19 pandemic: Pathophysiology and manifestations from the gastrointestinal tract

Table 1 Direct comparison between severe acute respiratory syndrome coronavirus, Middle East respiratory syndrome coronavirus and severe acute respiratory syndrome coronavirus 2, based on receptor usage, primary and intermediate host, incubation period, number of cases and deaths, and basic reproduction number (R0)

Virus	Receptor	Primary host	Intermediate host	Incubation period	Number of cases (Globally)	Number of deaths (Globally)	Fatality	R0
SARS-CoV	ACE2	Bats	Raccoon dogs and civets	Approximately between 2 d and 10 d, and up to 14 d	8000	800	10%	2-5
MERS-CoV	DPP4 (CD26)	Bats	Camels	Typically, between 2 d and 14 d	2500	800	35%	2-5
SARS-CoV-2	Most likely ACE2	Bats	Pangolin (Manis pentadactyla)	Current estimates between 3d to 7 d, and up to 14 d	Over 3349786 as of 03 May, 2020	Over 238628 as of 03 May, 2020	3.4% as of 3 March, 2020[37]	2-3.5

SARS-CoV: Severe acute respiratory syndrome coronavirus; MERS-CoV: Middle East respiratory syndrome coronavirus; SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2; ACE2: Angiotensin converting enzyme type 2.