Increase in bloodstream infections caused by emm1 group A Streptococcus correlates with emergence of toxigenic M1UK, Belgium, May 2022 to August 2023

Abstract: Many European countries have recently reported upsurges in invasive group A Streptococcus (iGAS) infections, mainly caused by emm 1 Streptococcus pyogenes , specifically the toxigenic M1 UK lineage. We present the epidemiology of emm 1 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 emm 1 S. pyogenes that continued into 2023.