Abstract
A Europe-wide outbreak of invasive pediatric group A streptococcal infections (iGAS) began in fall 2022. Here, we report the evolution of GAS hospitalizations in children and adolescents during the second outbreak year in 2023-2024 at a tertiary center in Switzerland. Using prospective monitoring of all in-patient GAS cases below 16 years of age, including those with iGAS, we compared case frequencies and clinical characteristics in three time periods (2013-2020; 2022-2023; 2023-2024). Annual GAS hospitalizations increased from a median of 25 cases (range 11-28) in 2013-2020 to 89 and 63 cases, respectively, in 2022-2023 and 2023-2024. iGAS cases evolved similarly (2013-2020, 4 cases (3-8); 2022-2023, 32 cases; 2023-2024, 21 cases). The decline in cases from 2022-2023 to 2023-2024 included all types of GAS organ involvement, except suppurative infections in the head area, which remained largely unchanged (48 vs. 45 cases). Pleural empyema declined from 13 to 7 cases, possibly explained by a poor overlap of the GAS and influenza curves, respectively, in 2023-2024 compared to 2022-2023. These data document the prolongation of the GAS outbreak into its second winter season in 2023-2024.