Socio-environmental and clinical features of invasive group A streptococcal disease in the Northern Territory of Australia.

Objective: To describe the socio-environmental profile and clinical features of invasive group A streptococcal (iGAS) infections in the Northern Territory (NT) of Australia over 10 years.

Methods: Cases of iGAS disease diagnosed between 1 May 2011 and 30 April 2021 were retrospectively identified from the NT Notifiable Diseases System and electronic health records accessed. Remoteness of residence, socio-economic index, seasonality and clinical characteristics were recorded.

Results: There were 692 cases of iGAS disease identified in the NT during the period 1 May 2011 - 30 April 2021. The age-standardised incidence of iGAS disease was significantly higher in people living in very remote (57.1 cases per 100,000 population, 95% confidence interval [95% CI]: 48.6-65.5) and remote areas (40.9 cases per 100,000 population, 95% CI: 34.7-47.2) than in outer regional areas of the NT (15.7 cases per 100,000 population, 95% CI: 13.4-17.9). People with socio-economic disadvantage were also disproportionately affected, with an incidence of 52.6 cases per 100,000 population (95% CI: 46.2-58.9) in decile 1-3 populations, compared to 8.9 cases per 100,000 population (95% CI: 6.9-10.9) for decile 7-10. For cases with recorded severity data, 135 of 378 (36%) met locally-defined criteria for severe iGAS disease. Recurrent iGAS disease was commonly observed in the dialysis cohort, affecting 17 of the 106 patients during the study period (16% recurrence rate) and causing two deaths. Five molecularly-confirmed clusters of iGAS disease were identified from the study period.

Conclusions: iGAS disease is unevenly affecting people in the NT. Those living in areas of socio-economic disadvantage, those in remote and very remote communities, and those receiving dialysis were most affected. It is important that primordial, primary and secondary prevention measures be directed towards supporting these disadvantaged population groups.