National Scottish surveillance data covering 3,408 invasive group A streptococcus infections between 2014 and 2024 were analysed alongside hybrid whole-genome sequencing of 404 emm1 isolates from invasive and tonsillitis cases. Incidence rose sharply in late 2022 and early 2023, disproportionately in children and older adults, coinciding with increased influenza and RSV circulation, but without a proportional rise in bacteraemia. Post-pandemic emm1 isolates were indistinguishable from pre-pandemic ones across genome-wide polymorphisms, accessory genes, mobile elements and structural variants.
Why it is interesting: Separates two explanations for a post-pandemic bacterial surge, attributing it to host susceptibility and viral co-infection rather than pathogen evolution.