Clinical characterization of an emm1-dominant group A Streptococcus outbreak in Chile in the context of the previous 6 years

These findings suggest that the Chilean outbreak was driven by the expansion of the <i>emm1</i> lineage rather than an increase in strain virulence. The identification of M1UK strains and the reduced <i>emm</i> diversity support a model of lineage introduction and clonal expansion. The significant clinical burden observed among h-niGAS cases underscores the importance of including hospitalized noninvasive infections in surveillance efforts. Ongoing integrated clinical and genomic surveillance of both iGAS and h-niGAS is essential to monitor emerging lineages and antimicrobial resistance trends.