The M-protein is a major virulence factor
for GAS and 80 variations of this protein have been identified to date,
through sequencing of the emm gene.9 M-subtypes of GAS are associated
with specific diseases; for example, M1 and M3 are linked with toxic
shock syndrome. However, the predominant M-types responsible for ARF
in North America and Europe are not the same as those isolated in Africa
and the Pacifi c, which has affected vaccine development for GAS