The epidemiology of superficial Streptococcal A (impetigo and pharyngitis) infections in Australia: A systematic review

Abstract

Background: Streptoccocal A (Strep A, GAS) infections in Australia are responsible for significant morbidity and mortality through both invasive (iGAS) and post-streptococcal (postGAS) diseases as well as preceding superficial (sGAS) skin and throat infection. The burden of iGAS and postGAS are addressed in some jurisdictions by mandatory notification systems; in contrast, the burden of preceding sGAS has no reporting structure, and is less well defined. This review provides valuable, contemporaneous evidence on the epidemiology of sGAS presentations in Australia, informing preventative health projects such as a Streptococcal A vaccine and standardisation of primary care notification.

Methods and findings: MEDLINE, Scopus, EMBASE, Web of Science, Global Health, Cochrane, CINAHL databases and the grey literature were searched for studies from an Australian setting relating to the epidemiology of sGAS infections between 1970 and 2020 inclusive. Extracted data were pooled for relevant population and subgroup analysis. From 5157 titles in the databases combined with 186 grey literature reports and following removal of duplicates, 4889 articles underwent preliminary title screening. The abstract of 519 articles were reviewed with 162 articles identified for full text review, and 38 articles identified for inclusion. The majority of data was collected for impetigo in Aboriginal and Torres Strait Islander populations, remote communities, and in the Northern Territory, Australia. A paucity of data was noted for Aboriginal and Torres Strait Islander people living in urban centres or with pharyngitis. Prevalence estimates have not significantly changed over time. Community estimates of impetigo point prevalence ranged from 5.5-66.1%, with a pooled prevalence of 27.9% [95% CI: 20.0-36.5%]. All studies excepting one included >80% Aboriginal and Torres Strait Islander people and all excepting two were in remote or very remote settings. Observed prevalence of impetigo as diagnosed in healthcare encounters was lower, with a pooled estimate of 10.6% [95% CI: 3.1-21.8%], and a range of 0.1-50.0%. Community prevalence estimates for pharyngitis ranged from 0.2-39.4%, with a pooled estimate of 12.5% [95% CI: 3.5-25.9%], higher than the prevalence of pharyngitis in healthcare encounters; ranging from 1.0-5.0%, and a pooled estimate of 2.0% [95% CI: 1.3-2.8%]. The review was limited by heterogeneity in study design and lack of comparator studies for some populations.

Conclusions: Superficial Streptococcal A infections contribute to an inequitable burden of disease in Australia and persists despite public health interventions. The burden in community studies is generally higher than in health-services settings, suggesting under-recognition, possible normalisation and missed opportunities for treatment to prevent postGAS. The available, reported epidemiology is heterogeneous. Standardised nation-wide notification for sGAS disease surveillance must be considered in combination with the development of a Communicable Diseases Network of Australia (CDNA) Series of National Guideline (SoNG), to accurately define and address disease burden across populations in Australia.

Trial registration: This review is registered with PROSPERO. Registration number: CRD42019140440.

Fig 1. Spectrum of Streptococcal A related disease and notification status in Australia.

The nomenclature for sGAS also remains diverse and the various terms used to describe this have been included in the figure for both skin and throat infection.

Fig 2. PRISMA flow chart.

Reported according to the PRISMA Protocol for the reporting of systematic reviews [16,18].

Fig 3. Demographics of included articles and studies.

(a) Population representation in included articles. Tan: Reporting only pharyngitis. Tan/blue overlay: Reporting on both impetigo and pharyngitis. Blue: Reporting on only impetigo. Green: Reporting on ≥80% First Nations population. ^aTwo studies were reported in Yeoh et al (2017) [62], with data collected prospectively and retrospectively; ^bTwo studies were reported in Charles et al (2004) [32], with data collected a decade apart; ^cDel Mar (1995) [36], included only extrapolated incidence data and was omitted from analysis of prevalence. (b) Geographical coverage of included articles. Number of articles covering specified territories within Australia; Western Australia excluding the Kimberley region, Western Australia including the Kimberley region, Northern Territory excluding Arnhem Land, Northern Territory including Arnhem Land, South Australia, Victoria, Tasmania, New South Wales, Australian Capital Territory and Queensland. (c) Year/mid-point year of data collection of included studies (n = 40).

Fig 4. The prevalence of impetigo diagnosed in a community setting, categorized by predominance of Aboriginal and Torres Strait Islander people in the study.

Aboriginal and Torres Strait Islander representation in study: Blue >80%, Tomato 20–80%. Climate: Reported according to Koppen Classification System [63,64].

Fig 5. The prevalence of impetigo diagnosed in a healthcare setting, categorized by predominance of Aboriginal and Torres Strait Islander people in the study.

Aboriginal and Torres Strait Islander representation in study: Blue >80%, Tomato 20–80%, Mustard <20%. Climate: Reported according to Koppen Classification System [63,64].

Fig 6. The prevalence of pharyngitis diagnosed in a community setting, categorized by predominance of Aboriginal and Torres Strait Islander people in the study.

Aboriginal and Torres Strait Islander representation in study: Blue >80%, Mustard <20%. Climate: Reported according to Koppen Classification System [63,64].

Fig 7. The prevalence of pharyngitis diagnosed in a healthcare setting, categorized by predominance of Aboriginal and Torres Strait Islander people in the study.

Aboriginal and Torres Strait Islander representation in study: Blue >80%, Mustard <20%. Climate: Reported according to Koppen Classification System[63,64].