Table 1.

Properties of SARS-CoV-2 variants (https://outbreak.info/).

Lineage	Earliest documented samples	Key mutations of spike protein	Transmissibility
Alpha (B.1.1.7)	UK, September 2020	DEL69/70, DEL144/145,N501Y	∼50 % increase in comparison with previously circulating strains [22], [23]
Beta (B.1.351)	South Africa, September 2020	L18F,DEL241/243, K417N,E484K,N501Y	50 % increase [26], [27], [28]
Gamma (P.1)	Brazil, December 2020	L18F,K417T,E484K,N501Y	1.4–2.2 times more transmissible [32]
Delta(B.1.617.2)	India, December 2020	G142D,E156G,DEL157/158,L452R,T478K	97 % increase [33], [34], [35], [36], [37], [38]
Omicron (B.1.1.529)	South Africa, November 2021	DEL143/145,S373P,S375F,K417N,S477N,T478K,E484A,Q493R,Q498R,N501Y,Y505H	Compared with Delta variant, the transmission of Omicron is enhanced [42]
Lambda(C.37)	Peru and Chile, April 2021	T76I, F490S and L452Q	Increased transmissibility relative to that of the parental Wuhan strain [43], [44], [45]
Mu (B.1.621)	Colombia, January 2021	E484K,N501Y,P681H,D614G	Mu is likely to be less transmissible than Delta [46], [47], [48]