Team Sees Tight Transmission Bottlenecks for SARS-CoV-2 Variant Lineages

University of Michigan researchers reporting in Nature Communications consider the transmission bottlenecks that affect the spread of new SARS-CoV-2 mutations, comparing the transmissibility and transmission bottlenecks associated with variant-of-concern (VOC) SARS-CoV-2 lineages such as Alpha, Delta, or Omicron with non-VOC lineages. With deep-sequencing on SARS-CoV-2 isolates from 168 SARS-CoV-2-infected individuals from 65 households in Michigan, the team tallied single nucleotide variants within viral populations and across transmission pairs, uncovering tight transmission bottlenecks for both VOC and non-VOC SARS-CoV-2 lineages. "We found that bottleneck size did not vary significantly between transmission pairs infected with pre-VOC lineages and those infected with highly transmissible Alpha, Delta, or Omicron (BA.1) lineages," the authors report. "This tight bottleneck estimate was driven by the limited diversity in the donor host at the time of transmission."