5e - Current surveillance system underestimated paediatric invasive Group A Streptococcal disease in Finland: a population registry-based study, 2014-2023

Background : Invasive Group A streptococcal infections (iGAS) in children have increased in several European countries after the COVID-19 pandemic. This trend was not observed in Finland, where iGAS surveillance is laboratory-based, Streptococcus pyogenes (GAS) findings confirmed by culture or PCR in blood or cerebrospinal fluid are notified to the National Infectious Disease Registry (NIDR). Other clinical presentations of iGAS are not under surveillance. Our aim was to identify paediatric clinical iGAS cases in the Hospital Discharge Registry (HDR) to assess the completeness of the current iGAS surveillance system.

Methods : We conducted a population registry-based study, including laboratory-confirmed iGAS cases from NIDR and clinical iGAS cases from HDR, aged 0-17 years and reported during 01.01.2014-31.12.2023. To identify iGAS cases in HDR we selected eleven ICD10-codes according to literature, among them A40.0 (GAS sepsis) and B95.0 (disease due to GAS). We used personal unique identifiers to assess overlap of iGAS cases in both registries.

Results : We identified 138 paediatric iGAS cases in NIDR and 135 cases in HDR. Of the HDR cases, 88 (65%) overlapped with NIDR cases. Of the 47 cases found only in HDR, 37 (79%) were coded as GAS sepsis, and 10 as other iGAS clinical presentations (pneumonia (n=4), arthritis (n=3), and cellulitis (n=3)). Combined, we identified 185 unique iGAS cases, representing an increase of 34% (47/138) compared to NIDR only.

Conclusions : Our study suggests that NIDR underestimated the number of paediatric iGAS cases during 2014-2023, especially for GAS sepsis. A comprehensive evaluation of the iGAS surveillance system is warranted to tackle underreporting and gain better insight into the paediatric iGAS burden in Finland. This might facilitate identification of at-risk groups and the implementation of targeted prevention measures.