 Increasing reports of invasive streptococcus pyogenes infections mandate surveillance for toxogenic lineage M1UK. An allyl-specific PCR was developed to distinguish M1UK from other M1 strains. The M1UK lineage represented 91% of invasive M1 isolates in England in 2020. Allyl-specific PCR will permit surveillance for M1UK without need for genome sequencing. This article was authored by Sean Yun Ji, Ho Kwon Lee, Han Chi Lee, and others.