Risk and determinants of mortality associated with invasive group A streptococcus (iGAS) disease in Scotland: a national surveillance study.

Objectives: Understanding determinants of mortality in invasive Group A Streptococcal (iGAS) infections is essential for developing targeted public health measures and improving clinical management. Using a comprehensive prospectively-collected national surveillance dataset, we set out to investigate factors associated with case fatality in Scotland.

Methods: We included all episodes of iGAS notified in Scotland surveillance data from January 2017 to December 2024. Case fatality was ascertained by seven-day follow up. Regression models incorporating key clinical, microbiological, and demographic predictors were constructed to investigate factors associated with higher case fatality.

Results: There were 2,209 iGAS notifications, of whom 191 died (8.6%). In multivariate analysis, increasing age (OR for 45-64 years: 2.36 [CI95%:1.3-4.48]; OR for 65-74 years: 4.54 [2.41-8.89]; and OR for 75 years and over: 7.77 [3.4-14.8]; emm type 3.93 (OR: 3.13 [1.43-6.76]) and emm type 1 (3.44 [2-6.15]); alcohol misuse (2.56 [1.36-4.63]); respiratory tract infection (2.07 [1.27-3.32]); and intensive care admission (2.5 [1.7-3.66]) were all significantly associated with mortality.

Conclusions: Case fatality from iGAS was high, particularly for vulnerable populations, and for those with emm type 3.93 and emm type 1 infections. Novel clinical, therapeutic, and public health interventions to improve clinical outcomes are required.