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Characterization of emerging Strains of SARS-Cov-2

Viruses have an inherent property of undergoing genetic reassortment from time and then to keep evolving. SARS-Cov-2 virus responsible for causing severe acute respiratory disease (COVID-19) has mutated into multiple variants since its first appearance in December 2019 in China. Majority of mutations seldom impact the properties of virus, but some may turn into extremely virulent strains. WHO has characterized SARS-Cov-2 variants into a) Variant of Interest and b) Variant of Concern depending upon the degree of risk posed on the global public health (Aleem et al., 2022; Khandia et al., 2022)

a) Variant of Interest (VOI) (Aleem et al., 2022)

SARS-Cov-2 Variants associated with increased transmissibility or virulence, diagnostic evasion, lower neutralisation by natural or vaccine-produced antibodies, or a decreased vaccine efficacy are classified as Variant of Interest (Aleem et al., 2022). The WHO has identified eight variants of interest (VOIs) since the beginning of the pandemic as:

i.Epsilon (B.1.427 and B.1.429): This variant was reported from US in June 2020. Compared to wild-type strain, it showed an increased transmissibility

ii. Zeta (P.2): was discovered for the first time in Brazil in April 2020. This was designated as VOI because of its reduction in neutralization by antibody therapy and immunisation.

iii. Eta (B.1.525): was discovered in November 2020 in New York. WHO and CDC identified them as a variant of interest due to their reduced neutralisation by antibody therapies and vaccine.

iv. Theta (P.3): was identified for the first time in Philippines and Japan in February 2021. WHO categorized them as VOI.

v. Iota (B.1.526): was designated by CDC as VOI

vi. Kappa (B.1.617.1): was first discovered in India in December 2021. The WHO and the CDC designated Kappa as variant of interest.

vii. Lambda (C.37): was identified in Peru for the first time and classified as VOI by WHO.

viii. Mu (B.1.621): was identified in Columbia for the first time and classified as VOI by WHO.

b) Variant of Concern (VOC):

Variant of Concern fulfils all the requirements of VOI, but VOCs pose a greater threat of transmissibility, harmful impacts on epidemiology, increased virulence or variability in clinical presentation, and decreased diagnostic, therapeutic, and vaccine interventions (Khandia et al., 2022).

WHO has identified five Variants of Concern describes as:

i. Alpha (B.1.1.7): first variant of concern described in the United Kingdom (UK) in late December 2020. It was reported to be 43% to 82% more transmissible. Initial case-control studies reported it to be not associated with higher risk of hospitalization or mortality compared to other then circulating strains. But, later it was confirmed to be associated with higher disease severity due to this strain (Aleem et al., 2022).

ii. Beta (B.1.351): first reported in South Africa in December 2020. This variant is reported to have an increased risk of transmission and reduced neutralization by monoclonal antibody therapy, convalescent sera, and post-vaccination sera (Aleem et al., 2022).

iii. Gamma (P.1): The third variant of concern, first reported in Brazil in early January 2021. This variant has reduced neutralization by antibody therapies, convalescent sera, and post-vaccination sera (Aleem et al., 2022).

iv. Delta (B.1.617.2): The fourth variant of concern, first reported in India in December 2020. It was responsible for the catastrophic second wave of COVID-19 infections in India in April 2021. Initially, the Delta variant was categorised into variant of interest but, due to its rapid spread over the world, the WHO classified this strain as a VOC in May 2021 (Aleem et al., 2022).

v. Omicron (B.1.1.529): The fifth variant of concern, first reported in South Africa in November 2021. Omicron was classified into VOC due to high number of mutation (>30) in its spike protein and sharp increase in cases in South Africa. Omicron was found to be 2.8 times more virulent than delta strain. Antibodies are believed to have reduced efficacy against Omicron variant (Aleem et al., 2022)

References:

• Aleem, A., Samad, A.B.A., Slenker, A.K., 2022. Emerging Variants of SARS-CoV-2 And Novel Therapeutics Against Coronavirus (COVID-19), StatPearls [Internet]. StatPearls Publishing.

• Khandia, R., Singhal, S., Alqahtani, T., Kamal, M.A., El-Shall, N.A., Nainu, F., Desingu, P.A., Dhama, K., 2022. Emergence of SARS-CoV-2 Omicron (B.1.1.529) variant, salient features, high global health concerns and strategies to counter it amid ongoing COVID-19 pandemic. Environmental Research 209, 112816. https://doi.org/10.1016/j.envres.2022.112816

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