Virulence and infectivity were associated with different fragments in the Delta subtype of SARS-CoV-2

Since 2019, the antigens from Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) have evolved from the initial D614 wild strain in the first epidemic wave, to D614G mutant in the second wave, to Delta mutant in the third wave, and to Omicron mutant in the fourth wave. Were the virulence and infectivity associated with different fragments in the Delta subtype of SARS-CoV-2? It is needed to analyze the sequences of the virus. The longest four glycine-free antigen fragments with tryptophan, longer or equal to 37 amino acids in length, were selected. The four fragment sequences in D614, D614G, N148, and I358 Omicron subtype were searched from the National Center of Biological Information website. The standard deviation (SD) of the molecular weight of the contained amino acids in the fragments was calculated to be the indicator of their antigen precession. The longest fragment was analyzed for the relationship between antigen precession and virus infectivity. On the other hand, 10 mutations in the Delta subtype were found in eight mutated fragments, and their antigen precession was used to analyze the correlation with virus virulence. The longest antigen fragments determined virus infectivity. Whole mutated fragments determined the virulence. Both were associated with different mutated fragments with varied antigen precession in the Delta subtype of SARS-CoV-2.