Rapid expansion and international spread of M1UK in the post-pandemic UK upsurge of Streptococcus pyogenes

Abstract The UK observed a marked increase in scarlet fever and invasive group A streptococcal infection in 2022 with severe outcomes in children and similar trends worldwide. Here we report lineage M1 UK to be the dominant source of invasive infections in this upsurge. Compared with ancestral M1 global strains, invasive M1 UK strains exhibit reduced genomic diversity and fewer mutations in two-component regulator genes covRS . The emergence of M1 UK is dated to 2008. Following a bottleneck coinciding with the COVID-19 pandemic, three emergent M1 UK clades underwent rapid nationwide expansion, despite lack of detection in previous years. All M1 UK isolates thus-far sequenced globally have a phylogenetic origin…

• NI
  National Institute for Health Research Health Protection Research Unit
• NI
  National Institute for Health and Care Research
• DO
  Department of Health and Social Care
• UO
  University of Warwick
• IC
  Imperial College London
• IC
  Imperial College Healthcare NHS Trust
• RT
  Rosetrees Trust
• PH
  Public Health England
• DF
  Department for International Development

  Award: MR/T016434/1
• MR
  Medical Research Council

  Awards: MR/X001962/1, MR/P022669/1, MR/R015600/1, MR/T016434/1, MR/P022669/1, MR/X001962/1, MR/X007421/1, MR/T016434/1
• NI
  NIHR Imperial Biomedical Research Centre
• CF
  Center for Molecular Biosciences, University of Innsbruck