Lynskey NN, Jauneikaite E, Li HK, et al. - In view of the unexpected elevation in invasive Streptococcus pyogenes infections in coincidence with England's scarlet fever seasonal rise in 2016, researchers sought to delineate the molecular epidemiological investigation of these events. They used regional (northwest London) and national (England and Wales) data to analyze shifts in S pyogenes emm genotypes, and notifications of scarlet fever and invasive disease in 2014–16. Outcomes revealed that during increased S pyogenes activity in England, there was an emergence of dominant new emm S pyogenes lineage (designated M1_UK) distinguished by increased SpeA production. An apparent fitness advantage of the new M1_UK lineage within the population was noted, it manifested during the scarlet fever seasons of 2015 and 2016. As per phylogenetic analysis, the dominant cause of invasive S pyogenes infections was the emergent lineage in England in 2016; isolates from symptomatic throat infections and scarlet fever describe the major reservoir for invasive infections. The data thereby support a possible role of transmission of virulent emm strains with enhanced ability to cause scarlet fever in the contemporaneous rise in invasive S pyogenes disease.