INVASIVE group A streptococcal (iGAS) infections in children have significantly increased in Ontario over recent years, particularly following the COVID-19 pandemic, according to a new 32-year case series.
Researchers conducted population-based surveillance of all paediatric iGAS cases from 1992 to 2023 across Toronto and the Peel Region. Using data from Statistics Canada and emm typing from the National Microbiology Laboratory, they analysed clinical presentations, disease severity, and infecting emm types in 498 cases among children under 18.
The study revealed that iGAS incidence rose from 1.8 per 100,000 children annually in 1992–2011 to 2.4 per 100,000 in 2012–2019 (incidence rate ratio: 1.3, 95% CI: 1.1–1.6), largely due to respiratory tract infections. Incidence dropped during the pandemic (1.2 in 2020; 0.5 in 2021) but surged to 6.0 in 2023. Of the recent cases, 32% had a respiratory viral coinfection. The most common clinical presentations were soft tissue infections (28.1%) and bacteraemia without focus (26.3%). Severe outcomes included streptococcal toxic shock syndrome (5.8%), necrotising fasciitis (2.4%), and a mortality rate of 2.0%.
Emm1 was the dominant strain (38.6%), with the M1UK variant accounting for 70% of emm1 isolates from 2019 onward. Emm1 was significantly linked to pneumonia (OR: 1.99, 95% CI: 1.16–3.40) and ICU admission (OR: 1.67, 95% CI: 1.03–2.68), while emm4 was linked to isolated bacteraemia (OR: 6.10, 95% CI: 2.83–13.16). Varicella-associated iGAS dropped sharply following routine varicella vaccination in 2004, from 16.8% in the 1990s to under 1% post-2012.
These findings emphasise a concerning resurgence of paediatric iGAS, with respiratory viral coinfections playing a potential role. The high coverage of circulating emm types by the investigational 30-valent GAS vaccine offers hope for future prevention strategies.
Reference
Dabaja-Younis H et al; Toronto Invasive Bacterial Diseases Network. Invasive Group A Streptococcal Infection in Children, 1992-2023. JAMA Netw Open. 2025;8(4):e252861.
