Infectious Disease · Public Health · 3 h ago
M1 Lineages Drive Japan’s Post-COVID Streptococcal Toxic Shock Resurgence
A nationwide laboratory-based study analyzed 919 isolates from streptococcal toxic shock syndrome cases in Japan during 2023–2024. M1 UK and M1 13SNPs lineages accounted for most emm1 isolates; M1 13SNPs was associated with higher mortality in unadjusted analyses.
- M1 lineages accounted for 51.1% of isolates.
- M1 UK and M1 13SNPs predominated among emm1 isolates.
- M1 13SNPs mortality association was not adjusted for confounders.
Researchers analyzed 919 *Streptococcus pyogenes* isolates from laboratory-confirmed streptococcal toxic shock syndrome (STSS) cases reported across Japan in 2023–2024. The isolates represented 62.2% of 1,477 reported cases. The study used molecular typing to characterize emm types and emm1 sublineages and compared patient age and deaths across groups.
The emm1 type was found in 470 isolates (51.1%). Of these, 234 (49.8%) were M1 UK, 176 (37.4%) were M1 13SNPs, and 60 (12.8%) were M1 global. Compared with 2019, M1 UK and M1 13SNPs had increased while M1 global declined. Patients with M1 13SNPs had a higher mortality rate than patients with non-emm1 infections (31.3% vs. 23.2%; OR 1.51, 95% CI 1.02–2.22). The M1 13SNPs group was also younger on average than the non-emm1 group.
The findings document rapid lineage shifts and support continued molecular surveillance. The mortality association is exploratory: the study covered STSS cases only, had incomplete case coverage and clinical data, and did not adjust for potential confounders such as underlying conditions, treatment, or disease severity. The article is an early-release version and may be revised.
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Emerging Infectious Diseases: Post–COVID-19 Expansion of Streptococcus pyogenes Lineages Causing Toxic Shock Syndrome, Japan, 2023–2024 ↗This is an automated AI-condensed summary that has not yet been reviewed by an editor. Always consult the full item at the original source.