Increased burden of invasive group A streptococcal disease among Australian children, 2023–2024: a prospective cohort study

Background: (iGAS) disease surged from September 2022, exceeding pre-COVID-19 pandemic levels, showing atypical seasonality and disproportionately affecting children. We previously described the epidemiology of iGAS among Australian children from mid-2018 to end 2022 using data from the Paediatric Active Enhanced Diseases network and here provide updated clinical epidemiology for 2023 and 2024 to help inform public health strategies. Methods: Prospective surveillance of 0-17-year-olds with iGAS admitted to six tertiary hospitals in five Australian states/territories in 2023 and 2024. Confirmed cases had GAS detected from ≥1 sterile site specimen; probable cases had detection of GAS in ≥1 non-sterile site specimen and diagnosis of septic shock, streptococcal toxic shock syndrome or necrotising fasciitis. Findings: In 2023, the annualised incidence was 5.10 per 100,000 (95% CI 4.50-5.75, n = 263 cases) and dropped significantly in 2024 (annualised incidence 2.13, 95% CI 1.75-2.57, n = 111 cases). Quarter three peaks were not as predominant across 2023 and 2024 compared to usual patterns. Intensive care unit admission occurred among 147/374 (39%) children with six deaths. At discharge, 137/374 (37%) had not returned to premorbid function. Respiratory virus co-infection was found among 133/267 (49.8%) patients tested and was associated with higher risk of severe disease, RR 1.6 (95% CI 1.26-2.07). Adjunctive clindamycin, linezolid or intravenous immunoglobulin was used in 201/374 (54%), including 126/147 (86%) of severe disease cases. Interpretation: We have captured the end of post-COVID-19 pandemic iGAS surge in sentinel Australian paediatric hospitals. High iGAS incidence peaked in 2023, before reducing to similar pre-pandemic incidence in 2024. The dynamic epidemiology and persistent burden of disease highlight the need for continued vigilant public health efforts, surveillance, and vaccine development. Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.