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TORONTO, Canada – Invasive Group A streptococcal (iGAS) infections among children saw a dramatic surge in 2023, following a significant drop during the COVID-19 pandemic, according to a comprehensive 32-year study published on April 1, 2025, in JAMA Network Open. The research, based on Canadian surveillance data, highlights a particularly sharp increase driven by respiratory tract infections like pneumonia.
Researchers tracked iGAS cases in children from January 1, 1992, to December 31, 2023, analyzing data from 498 children (median age 5.1 years) treated in hospitals within a specific Canadian region.
The study revealed a concerning trend: after remaining relatively stable for two decades (average annual incidence of 1.83 and 1.70 events per 100,000 children from 1992-2001 and 2002-2011, respectively), the rate began to climb, averaging 2.38 from 2012 to 2019. During the height of COVID-19 restrictions in 2021, the incidence plummeted to just 0.51 cases per 100,000. However, this respite was short-lived, as the rate exploded to 6.05 in 2023 – more than double the pre-pandemic peak.
“The post-pandemic surges in GAS infections… should serve as a clarion call for a renewed emphasis in active pathogen surveillance, the study of transmission dynamics, and pathogen emergence,” warned the authors of an invited commentary accompanying the study.
The research also identified key patterns and risk factors:
- Respiratory Infections Drive Surge: The incidence of iGAS infections originating in the respiratory tract, particularly pneumonia, significantly increased over time and contributed heavily to the 2023 surge.
- Viral Co-infections Matter: Children under five who tested positive for a respiratory virus were dramatically more likely (Odds Ratio [OR] 28.11) to develop iGAS pneumonia compared to those who tested negative for viruses.
- Age-Specific Risks: Younger children (under 5) were more prone to having had chickenpox recently (OR 5.61) or developing bloodstream infections without a clear source (bacteremia without focus, OR 1.92). Children aged 5-9 were more likely to present with bone or joint infections (OR 2.19).
- Specific Strains Linked to Outcomes: The emm1 strain of Group A Strep was associated with a higher likelihood of pneumonia (OR 1.99) and bone/joint infections (OR 1.70), while the emm4 strain was strongly linked to bacteremia without focus (OR 6.10).
The study authors, led by Dr. Halima Dabaja-Younis from Sinai Health in Toronto, emphasized the practical implications. “This study also emphasizes the importance of considering age-specific factors in the clinical presentation of iGAS infections, reinforces the value of varicella [chickenpox] vaccination in preventing iGAS, and highlights the potential for both respiratory viral and GAS vaccines to alleviate the burden of iGAS infections,” they wrote.
While providing valuable insights, the study acknowledged limitations, including its focus on a single geographic area in Canada, potentially incomplete data from medical records, and the inability to include data from children deceased upon arrival at healthcare facilities.
The research received support from the Centers for Disease Control and Prevention and the Canadian Bacterial Diseases Network. The authors reported no conflicts of interest.
Disclaimer: This news article is based on findings from a study published in JAMA Network Open. It summarizes key information but is not a substitute for reading the original research or consulting with qualified healthcare professionals. The study has limitations, including its geographic focus, which may affect the generalizability of the results to other populations or regions.
