Table 1.

Summary of severe acute respiratory syndrome coronavirus 2 strains and mutations that enhance viral entry into the host cell

Sr. No.	Strain	Mutation	Host entry	Location	Time of first report	Ref.
1	Alpha (B.1.1.7)	N501Y mutation on the RBD	The affinity between RBD and ACE2 is significantly increased	United Kingdom	December 2020	[40-42]
2	Beta (B.1.351)	N501Y mutation on the RBD N417/K848/Y501	The affinity between RBD and ACE2 is significantly increased	South Africa	December 2020	[41-43]
3	Gamma (P.1)	N501Y mutation on the RBD N417/K848/Y501	The affinity between RBD and ACE2 is significantly increased	Brazil	January 2021	[41,42,44]
4	Delta (B.1.617.2)	Absence of N501Y mutation	No effect	India	December 2020	[41,42]
5	Omicron (B.1.1.529)	N501Y mutation on the RBD	The affinity between RBD and ACE2 is significantly increased	South Africa	November 2021	[41,42]

RBD: Receptor binding domain; ACE2: Angiotensin-converting enzyme 2.