Anomalous US-wide prevalence of reversion mutants in the emergence of Omicron BA.1

Surface glycoprotein sequences of the Omicron BA.1 lineage that include only reverse mutations were searched in NCBI GenBank, where the dates and the locations of collection were retrieved for each mutant. Data from BA.1.x lineages that appeared during the same period of time were used as a control, and the early spread of these mutants were compared. The number of states where the first 20 samples were found was compared between the group of reversion mutants and the control group. The result shows that the reversion mutants were widespread from the early days of their emergence, which shows statistically significant differences compared to the control group. Whether the origin of a mutant is natural infection from abroad, domestic natural mutation, or leakage from a laboratory, it is usually possible to make a rough estimation of the epicenter by tracing its spread. The wide prevalence of reversion mutants of BA.1 from the beginning of their emergence is highly anomalous and extremely unlikely to occur without human intervention.

Data available at https://visual-media-lab.github.io/data/BA1reversions/index.html