Genomic Surveillance Reveals the Rapid Expansion of the XBB Lineage among Circulating SARS-CoV-2 Omicron Lineages in Southeastern Wisconsin, USA.

SARS-CoV-2 caused a life-threatening COVID-19 pandemic outbreak worldwide. The Southeastern Region of Wisconsin, USA (SERW) includes large urban Milwaukee and six suburban counties, namely Kenosha, Ozaukee, Racine, Walworth, Washington and Waukesha. Due to the lack of detailed SARS-CoV-2 genomic surveillance in the suburban populations of the SERW, whole-genome sequencing was employed to investigate circulating SARS-CoV-2 lineages and characterize dominant XBB lineages among this SERW population from November 2021 to April 2023. For an unbiased data analysis, we combined our 6709 SARS-CoV-2 sequences with 1520 sequences from the same geographical region submitted by other laboratories. Our study shows that SARS-CoV-2 genomes were distributed into 357 lineages/sublineages belonging to 13 clades, of which 88.8% were from Omicron. We document dominant sublineages XBB.1.5 and surging XBB.1.16 and XBB.1.9.1 with a few additional functional mutations in Spike, which are known to contribute to higher viral reproduction, enhanced transmission and immune evasion. Mutational profile assessment of XBB.1.5 Spike identifies 38 defining mutations with high prevalence occurring in 49.8-99.6% of the sequences studied, of which 32 mutations were in three functional domains. Phylogenetic and genetic relatedness between XBB.1.5 sequences reveal potential virus transmission occurring within households and within and between Southeastern Wisconsin counties. A comprehensive phylogeny of XBB.1.5 with global sub-dataset sequences confirms the wide spread of genetically similar SARS-CoV-2 strains within the same geographical area. Altogether, this study identified proportions of circulating Omicron variants and genetic characterization of XBB.1.5 in the SERW population, which helped state and national public health agencies to make compelling mitigation efforts to reduce COVID-19 transmission in the communities and monitor emerging lineages for their impact on diagnostics, treatments and vaccines.

Genomic surveillance identifies SARS-CoV-2 transmission patterns in local university populations, Wisconsin, USA, 2020-2022.

Novel variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to emerge as the coronavirus disease 2019 (COVID-19) pandemic extends into its fourth year. Understanding SARS-CoV-2 circulation in university populations is vital for effective interventions in higher education settings and will inform public health policy during pandemics. In this study, we performed whole-genome sequencing of 537 of 1717 SARS-CoV-2-positive nasopharyngeal/nasal swab samples collected over a nearly 20-month period from two university populations in Wisconsin, USA. We observed that the viral sequences were distributed into 57 lineages/sub-lineages belonging to 15 clades, of which the majority were from 21K (omicron, 36.13 %) and 21J (delta, 30.91 %). Nearly 40 % (213) of the sequences were omicron, of which BA.1 and its eight descendent lineages accounted for 91 %, while the remaining belonged to BA.2 and its six descendent lineages. Independent analysis of the sequences from these two universities revealed significant differences in the circulating SARS-CoV-2 variants. Phylogenetic analysis of university sequences with a global sub-dataset demonstrated that the sequences of the same lineages from the university populations were more closely related. Genome-based analysis of closely related strains, along with phylogenetic clusters and mutational differences, identified that potential virus transmission occurred within and between universities, as well as between the university and the local community. Although this study improves our understanding of the distinct transmission patterns of circulating variants in local universities, expanding genomic surveillance capacity will aid local jurisdictions not only in identifying emerging SARS-CoV-2 variants, but also in improving data-driven public health mitigation and policy efforts.