Increase in bloodstream infections caused by emm1 group A Streptococcus correlates with emergence of toxigenic M1(UK), Belgium, May 2022 to August 2023

Many European countries have recently reported upsurges in invasive group A Streptococcus (iGAS) infections, mainly caused by emm1 Streptococcus pyogenes, specifically the toxigenic M1(UK) lineage. We present the epidemiology of emm1 causing iGAS in Belgium during 2018-August 2023, and describe an emergence of the toxigenic M1(UK) lineage in Belgium in mid-2022 that was observed as an increase in bloodstream infections caused by emm1 S. pyogenes that continued into 2023.