The evolution of the emerging SARS-CoV-2 variants carrying mutations in the spike protein raises concerns about the possibility of accelerated transmission in the ever-evolving COVID-19 pandemic worldwide. AY.4.2, a sublineage of the Delta variant, was considered a variant under investigation (VUI) and also gained the nickname "Delta Plus," due to its extra mutations, Y145H and A222V. In this study, using genomic epidemiology, we provide the first insights into the introduction of AY.4.2 in Bulgaria and the AY.4.2.1 sublineage that found larger dissemination only in Bulgaria and the United Kingdom.
Keywords: SARS coronavirus; epidemiology; mutation/mutation rate.
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