The Epidemiology and Outcomes of Invasive Group A Streptococcus (iGAS) Disease in North Queensland, Australia, 2000-2020 — The Association Specialists
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  3. The Epidemiology and Outcomes of Invasive Group A Streptococcus (iGAS) Disease in North Queensland, Australia, 2000-2020

The Epidemiology and Outcomes of Invasive Group A Streptococcus (iGAS) Disease in North Queensland, Australia, 2000-2020 (23601)

Himali Ratnayake 1 , Damon Eisen 1 , Oyelola Adegboye 2 , Anton Pak 3 , Emma McBryde 4
  1. James Cook University, Townsville, QLD, Australia
  2. Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
  3. Centre for Business and Economics of Health, The University of Queensland, Brisbane, Queensland, Australia
  4. Australian Institute of Tropical Health and Medicine, James Cook University, Townsville, Queensland, Australia

Background: Group A Streptococcus is a pathogen responsible for a wide spectrum of diseases, including life-threatening invasive conditions (iGAS). Globally, iGAS is recognised as one of the top 10 infectious causes of mortality. We aimed to describe the epidemiology and outcomes of iGAS in Northern Queensland, Australia.

Methods: Age and sex-standardized incidence rates, potential risk factors for the disease and outcomes, spatial distribution, and disease burden were analysed using a linked hospital data spanning for 21 years.

Results: 933 iGAS events were identified among 870 individuals. The mean age was 45 years (SD = 24.3). The highest burden was in infants and older adults. Males had a 31% higher incidence than females (95% CI: 1.13–1.52), and Indigenous individuals had a 9-fold higher incidence than non-Indigenous individuals (IRR = 9.33, 95% CI: 8.2–10.7). Sepsis was the most common diagnosis (60.5%). Streptococcal toxic shock syndrome (1.07%) and necrotising fasciitis (3.11%) were more frequent among non-Indigenous individuals. Spatial analysis demonstrated significant geographical clustering (Moran’s I = 0.19, z = 3.45, p < 0.001).

Case fatality rate was 5.2 % (45/870) and there were 219 (23%) intensive care unit admissions. Deaths due to iGAS declined overall across the study period, while case numbers continued to rise steadily. Most deaths were attributed to sepsis (80%) with necrotising fasciitis (18%) and septic shock (13.3%) also contributing. Competing Risks Regression showed higher mortality among individuals with renal failure (SHR = 3.3; 95% CI: 1.5-7.1), and non-Indigenous individuals (SHR = 2.5; 95% CI: 1.3–4.9). The total disability-adjusted life years attributable to iGAS was 1,375 years.  

Conclusion: iGAS represents a growing public health burden in Northern Queensland, with rising incidence despite declining mortality. Marked disparities in incidence and outcomes highlight the need for targeted prevention, early recognition, and improved management strategies, particularly for high-risk populations and geographically clustered regions.