8-year M type surveillance of Streptococcus pyogenes in China

Scarlet fever has been resurgent in China for more than 8 years. With ever more regions reporting increasing incidence, control of the outbreak throughout the country is challenging without an available vaccine.1You Y Davies MR Protani M et al.Scarlet fever epidemic in China caused by Streptococcus pyogenes serotype M12: epidemiologic and molecular analysis.EBioMedicine. 2018; 28: 128-135Summary Full Text Full Text PDF PubMed Scopus (47) Google Scholar Emergent Streptococcus pyogenes M types or subclones can lead to fatal outbreaks and are a huge threat to global public health.2Nasser W Beres SB Olsen RJ et al.Evolutionary pathway to increased virulence and epidemic group A streptococcus disease derived from 3615 genome sequences.Proc Natl Acad Sci USA. 2014; 111: e1768-e1776Crossref PubMed Scopus (181) Google Scholar We read with interest the Article by Nicola N Lynskey and colleagues3Lynskey NN Jauneikaite E Li HK et al.Emergence of dominant toxigenic M1T1 Streptococcus pyogenes clone during increased scarlet fever activity in England: a population-based molecular epidemiological study.Lancet Infect Dis. 2019; 19: 1209-1218Summary Full Text Full Text PDF PubMed Scopus (48) Google Scholar on the emergence of the dominant toxigenic M1T1 S pyogenes clone during increased scarlet fever activity in England. Lynskey and colleagues emphasise the need for molecular surveillance of S pyogenes for timely detection of emergent M types or toxigenic clones, which aids in the understanding of epidemic trends. Scarlet fever is a notifiable disease in China, but surveillance of S pyogenes M type is rarely involved.1You Y Davies MR Protani M et al.Scarlet fever epidemic in China caused by Streptococcus pyogenes serotype M12: epidemiologic and molecular analysis.EBioMedicine. 2018; 28: 128-135Summary Full Text Full Text PDF PubMed Scopus (47) Google Scholar Here we report an 8-year surveillance study of S pyogenes M type during 2011–18 in Beijing. 24 590 respiratory throat swab samples were collected from patients with scarlet fever and streptococcal infection; 2484 strains were isolated and analysed for emm type. Coincident with a decline in scarlet fever notifications in Beijing since 2012, the frequency of M12 S pyogenes started to decline from 2011, whereas M1 started to increase and then exceeded M12 in 2013 and 2014, when the scarlet fever incidence began to increase. Since 2014, non-predominant types have increased in frequency. Notably, numbers of M128 increased substantially in 2017 and of M3 in 2018 (figure; appendix). In view of these findings, we speculate that regional herd immunity against M12 serotype has become established in susceptible populations in Beijing. The increasing frequency of M1 is alarming, and epidemic trends of both scarlet fever and invasive S pyogenes infections caused by M1 should be given more attention. Furthermore, further population genetic analysis in a global context is required. The emergence of M128 and M3, and the increasing frequency of other non-predominant M types, reflect diversification of respiratory S pyogenes strains in Beijing. With no herd immunity, populations in Beijing are at high risk of scarlet fever epidemics caused by these types. This study was the first long-term and largest surveillance of S pyogenes M type in the past 8 years of scarlet fever resurgence in China. Public health facilities should pay increasing attention to M type shift. With more frequent domestic and global transportations, long-term, nationwide, active surveillance of M type is necessary to monitor the spread of emergent clones. YY and XP contributed equally. We declare no competing interests. Download .pdf (.09 MB) Help with pdf files Supplementary appendix Emergence of dominant toxigenic M1T1 Streptococcus pyogenes clone during increased scarlet fever activity in England: a population-based molecular epidemiological studyA dominant new emm1 S pyogenes lineage characterised by increased SpeA production has emerged during increased S pyogenes activity in England. The expanded reservoir of M1UK and recognised invasive potential of emm1 S pyogenes provide plausible explanation for the increased incidence of invasive disease, and rationale for global surveillance. Full-Text PDF Open Access