Tracing the recent evolution of Group A M1 serotype.

The twenty-first century has seen global surges in scarlet fever and invasive Group A (GAS) infections, partly driven by the emergence of the toxigenic M1 lineage. Characterized by increased SpeA superantigen expression and the stepwise accumulation of 27 single nucleotide polymorphisms (SNPs), M1 has become the dominant GAS 1 lineage in Europe, Australia and Canada, representing a notable shift in GAS molecular epidemiology. Interestingly, other distinct 1 variants have emerged in China and Denmark but are yet to expand globally in the same manner. This review examines the recent evolution of the GAS 1 lineage, with emphasis on genomic and molecular drivers, highlighting the ongoing diversification of this pathogen and the need for continued surveillance and research.