Invasive group A streptococcal infections in Australian adults – a descriptive cohort and cost burden study

Objectives: To describe the epidemiology, clinical course, genomics, and cost burden of hospital care of invasive group A streptococcal (iGAS) amongst adults (≥18 years) treated at the Royal Melbourne Hospital (RMH) during 2018-2023 and extrapolate findings to estimate the annual healthcare cost burden of treating adult iGAS cases in Australia. Methods: Retrospective cohort study and economic evaluation, including a single hospital cost burden analysis followed by a national cost extrapolation. Results: There were 79 eligible iGAS cases between 2018-2023. Seven cases were fatal (case fatality rate: 9%, 95% CI: 4%–18%), one third (29, 35%) were admitted to intensive care and one third (27; 38%) of non-fatal cases were discharged with an impairment. The average iGAS disease-related healthcare cost was $63,662 (SD $84,743) per person, with a combined healthcare utilisation cost for the cohort of $5,029,305. Most costs (80%) were incurred during the index admission. In 2023, the estimated national healthcare cost burden for adults with iGAS was $117.5 million. Conclusions: iGAS among adults in Australia generates a significant health and financial burden. Our findings highlight the importance of investment in research to prevent iGAS and identify the optimal treatment for this severe infection.