Background: In the absence of routine surveillance data, we explored the epidemiology of invasive and immunological disease caused by group A streptococcal (GAS) infection in Victoria, Australia.
Methods: All individuals who were hospitalised with or died from invasive GAS disease (iGAS), scarlet fever, acute rheumatic fever (ARF) or rheumatic heart disease (RHD) or presented to an emergency department with scarlet fever in Victoria, Australia from 2007–2017 were included. Individual records were linked across hospitalisation, mortality, emergency department and laboratory datasets. Victoria’s notifiable diseases dataset was examined to identify individuals with both iGAS and hepatitis C.
Results: Incidence rates were highest among people aged <5 years for scarlet fever, 10–14 years for ARF and ≥75 years for iGAS and RHD. Scarlet fever and iGAS were more common among males than females (IRR 1.29 [95%CI 1.17–1.43] and 1.21 [95%CI 1.11–1.32], respectively). Hospitalisation incidence was higher for Indigenous compared to non‐Indigenous people aged <40 years for ARF (IRR 4.9 [95%CI 2.4–10]) and RHD (IRR 3.8 [95%CI, 2.4–6.2]). People with hepatitis C had higher iGAS incidence than people without hepatitis C (IRR 5.55 [95%CI 4.58–6.74]). The case fatality rate for iGAS was 5.6%, higher among those aged ≥75 years (13.5%) and those co-infected with hepatitis C (9.1%). No sustained change in incidence was observed for any study condition.
Conclusion: Study findings will inform state and national surveillance for iGAS and will be used to advocate for more formal surveillance including clinical registers for scarlet fever, ARF and RHD in Victoria.