Introduction: The comparison of SARS-CoV-2 delta variant with other variants revealed 3 unique mutation sites, E156del, R158G, and T478K, which were indicated by red letter (Table 1 and.

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Method: Besides this mutation, there are two additional unique mutation sites of SARS-CoV-2 delta variant, E156del and R158G with red letters in the NTD of S1 region with no known functionality (Table 1).

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Method: The three unique mutation sites, E156del, R158G, and T478K in the SARS-CoV-2 delta variant must be investigated if a recent outbreak of COVID-19 depends on the mutation sites in the S gene of SARS-CoV-2 delta variant.

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Introduction: Recently, a rapidly transmitting variant emerged in India, namely- B.1.617.2 (Delta) with unique RBD mutations E484Q and L452R, two deletions (E156del and F157del) and a substitution (R158G) in the NTD, and 4 other mutations including D614G.

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Result: Similarly, the recent B.1.617.2 lineage possess 4 NTD mutation combination (T19R, E156del, F157del, and R158G).

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