The epidemiology of invasive group A streptococcal disease in Victoria, 2007–2017: an analysis of linked datasets

Abstract

nvasive group A streptococcal disease (iGAS), defined as GAS infection of a normally sterile site, is associated with significant morbidity and mortality. 1 Necrotising fasciitis and toxic shock syndrome are particularly severe forms of iGAS, with case fatality rates ranging from approximately 20-50%. 1,2 Complex medical and surgical care is often required. 1 Certain groups have an increased risk of iGAS, particularly the very young and old. 1 Household contacts of iGAS cases are at a higher risk of secondary infection than the general population, 3,4 with a Victorian study reporting an incidence rate ratio of 2,011 (95%CI: 413-5,929) for the 30 days following onset of disease in the index case, 5 and a UK study reporting a similar incidence rate ratio of 1,940 (95%CI:1,240-2,880). 3 Chemoprophylaxis to prevent secondary disease in close contacts is recommended in Canada, 6 but not in the UK 7 or US. 8 Australia has no national guidelines for the prevention of secondary disease with antibiotic prophylaxis, though some Australian sources, including the Royal Children's Hospital in Melbourne, recommend antibiotic prophylaxis for close contacts. [9][10][11] Inequitably high rates of iGAS for Aboriginal and Torres Strait Islanders in Australia have been demonstrated, with annual incidence of 69.7 (95%CI: 51.6-92.0), 79.9 (95%CI: 62.6-97.2) and 82.5 per 100,000 population reported in the Northern Territory, 12 Western Australia 13 and North Queensland, 14 respectively. A paediatric cohort study with sites in six states and territories also found that the incidence of iGAS was 2.1-fold higher for Aboriginal and Torres Strait Islander children. 15 The last statewide characterisation of iGAS in Victoria was published in 2007 and used data from 2002 to 2004, reporting a mean annual incidence of 2.7 (95%CI: 2.3-3.2) per 100,000 population. 16 A more recent study that assessed the trends in iGAS from 2007 to 2017 reported a mean annual incidence of 2.1 (95%CI: 1.8-2.5) per 100,000 population, with a peak incidence of 3.6 (95%CI: 3.2-4.1) cases per 100,000 population in 2017. However, the study did not include all cases in the state and had no clinical or outcome data. 17 iGAS was added to the National Notifiable Diseases List (NNDL) in Australia in July 2021, 18 paving the way for it to become nationally notifiable. Previously it was

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside

“…Recent analyses report an increasing incidence of S. pyogenes infections with a high case fatality in the older population (Shakoor et al, 2017;Meehan et al, 2018;Blagden et al, 2020;Vilhonen et al, 2020;Bläckberg et al, 2022;Thomson et al, 2022). The most prevalent form of clinical presentation of invasive S. pyogenes infection is bacteremia (75%), followed by focus without bacteremia (19%) and necrotizing fasciitis (7%; Meehan et al, 2018).…”

Reducing the burden of group A streptococcal disease in the Northern Territory: the role of chemoprophylaxis for those at greatest risk

“…The iGAS disease burden in the NT reported by Birrell and colleagues is staggering. In the sparsely populated desert regions of Central Australia, the annual incidence was 82.2 cases per 100 000 population (95% confidence interval [CI], 71.8–92.7 per 100 000), 3.5 times as high as for the tropical Top End (23.2 [95% CI, 20.6–25.8] cases per 100 000 population), 1 and 26 times as high as the recently reported incidence in Victoria (3.1 [95% CI, 2.4–5.2] cases per 100 000 population) 3 . The incidence among Indigenous people was more than seven times as high as for non‐Indigenous Territorians, 1 consistent with Australian and overseas literature on iGAS disease in First Nations peoples 4‐6 .…”

Insights gained from sequencing Australian non-invasive and invasive Streptococcus pyogenes isolates

“…However, First Nations peoples are still disproportionately affected; with an estimated incidence of approximately 374 cases of acute rheumatic fever per 100 000 persons per year in the Pacific and Indigenous Australia and New Zealand combined [10]. Although, the true overall incidence of GAS infection in Australia is unknown [7,11,12], the health impact is substantial with iGAS, rheumatic heart disease and GAS-associated kidney disease estimated to cost approximately AU$185.1 million (£97.4 million; £1=AU$1.9) and cause 110 deaths annually [13].…”

“…Clinical cases of iGAS and/ or laboratory isolation of GAS from sterile sites were made nationally notifiable through local Public Health Units in Australia in 2022 [15,16]. This decision, in part, was made to better understand the dynamics of iGAS including the recent increases in Australia [7,11,12,14], detect outbreaks and assess preventative strategies. Current control guidelines for iGAS within NSW include molecular typing for suspected outbreaks [16].…”