P-1290. Invasive group A streptococcal infection in children in Toronto, Canada
Authors: Younis Halima Dabaja , Johnstone Jennie , Zhong Zoe , Kassee Caroline , Allen Vanessa , Armstrong Irene , Baqi Mahin , Barker Kevin R , Bitnun Ari , Borgia Sergio , Campigotto Aaron , Chakrabarti Sumon , Gold Wayne , Golden Alyssa , Kandel Christopher , Kitai Ian , Kus Julianne , Macdonald Liane , Martin Irene , Muller Matthew , Nadarajah Jeya , Ricciuto Daniel R , Richardson David , Saffie Medina , Tadros Manal , Varia Monali , Hassan Kazi , Lefebvre Maxime , Li Angel , Sultana Asfia , Crowl Gloria , Farooqi Lubna , Pejkovska Mare , Malik Nadia , Barati Shiva , Vikulova Tamara , McGeer Allison 
Published: January 2025

Abstract

Background
Rising cases of invasive group A streptococcus (iGAS) in children have been reported globally. We assessed the epidemiology of pediatric iGAS over three decades.
The annual incidence of invasive GAS infections in children in Toronto and Peel Region during the years 1992-2023

Methods
Since 1992, the Toronto Invasive Bacterial Diseases Network has conducted surveillance for iGAS in Toronto/Peel Region, Canada. The National Microbiology Laboratory provides emm typing, and Statistics Canada supplies population data. iGAS data were analyzed by age group—toddlers (0-4 yrs), young children (5-9 yrs), and older children (10-17 yrs)— and over time from 1992 to 2024.
emm types in pediatric cases per 100,000 population in Toronto and Peel Region from 1992 to 2023.

Results
506 pediatric iGAS cases were identified. Figure 1 shows the incidence by age group. 61% of cases were male; 33% had underlying conditions. Main presentations were soft tissue infection (30%), bacteremia with no focus (22%), bone/joint infections (20%) and pneumonia (16%). Streptococcal toxic shock syndrome (STSS) occurred in 5.7% of cases, and necrotizing fasciitis (NF) in 2.6%. Positive blood cultures were found in 71% of cases, with additional sterile site cultures in 20%. emm1 (42%) and emm12 (16%) were the most common types (Figure 2), with M1UK comprising 63% of emm1 isolates in 2022/2023.
During the period of pandemic restrictions (Mar 2020-Apr 2022), iGAS cases declined, and emm1 disappeared. As restrictions eased, emm1 and, to a lesser extent, emm12 rebounded (Figure 3). Seasonality, with increased winter/spring cases, became more pronounced (Figure 4).
Toddlers had higher rates of bacteremia without focus (27% vs. 14%, p=0.01) and emm12 (20% vs. 8.4%, p=0.02) than older children. Younger children had higher rates of bone/joint infections than toddlers (28% vs. 16%, p=0.004).
Rates of STSS, NF, and 30-day mortality were consistent across age groups and time, with no association to specific emm types, except for higher mortality in emm4 [12.5% vs. 3.6%, OR 3.8 (1.2-12.1)]. Increasing pneumonia rates over time were associated with emm1. In multivariate analysis, pneumonia [OR 7.2 (2.9-17.6)], NF [OR 15.5 (4.2-58)], and increased age [OR 1.8 (1.03-3.2)] predicted STSS.
Monthly pediatric iGAS cases in relation to pandemic public health restrictions in Toronto and Peel Region from April 2018 to March 2024.

Conclusion
The recent rise in pediatric iGAS infections is a public health concern. Incidence has increased, but severity remains unchanged. emm1 transmission seems more susceptible to control by public health measures. Continuous surveillance is essential.
Seasonality of iGAS in children in Toronto/Peel region, 1992-2023

Disclosures
Allison McGeer, MD, AstraZeneca: Honoraria|GSK: Honoraria|Merck: Honoraria|Moderna: Honoraria|Novavax: Honoraria|Pfizer: Grant/Research Support|Pfizer: Honoraria|Roche: Honoraria|Seqirus: Grant/Research Support|Seqirus: Honoraria