Volume 218 - Issue 8
Reducing the burden of group A streptococcal disease in the Northern Territory: the role of chemoprophylaxis for those at greatest risk
Authors: Johanna M Birrell, Bart J Currie and Vicki L Krause
Med J Aust 2023; 218 (8): 380-380. || doi: 10.5694/mja2.51912
Published online: 1 May 2023
Published online: 1 May 2023
To the Editor: We thank Gibney and Steer for their editorial1 in response to our research letter,2 supporting further public health action and research into invasive group A streptococcal (iGAS) disease.
However, we are concerned about the statement that the 30‐day risk of iGAS disease for contacts of someone with an index infection is about 2000‐fold higher than background risk. This figure is derived from an English population‐based study3 and cannot be universally applied across circumstances varying in background incidence of GAS‐related disease, which is driven predominantly by socio‐environmental factors.
Applying this 30‐day secondary attack rate of iGAS infection in Northern Territory household contacts would translate to about 177 cases per 1000 population (18%) in Indigenous Australian contacts and 2738 per 1000 population (274%) in people receiving haemodialysis.2 In contrast, rates of iGAS infection in household contacts were 3.2 per 1000 population in Canada4 and 0.7 per 1000 population in the United States.5
As described in the NT public health guidelines for iGAS, previous NT and Queensland studies have demonstrated large diversity of iGAS genotypes,6 with less clonality and a greater proportion of sporadic cases rather than transmission directly from another case of iGAS infection. This reflects the stark contrasts in iGAS and other consequences of GAS infection between central and northern Australia and southern states, as seen with so many other health issues linked to socio‐economic disadvantage.
Gibney and Steer also note that some authorities recommend antibiotic prophylaxis for close contacts, and others do not.1 We wish to highlight that the NT guidelines for the public health response to iGAS include specific guidance around antibiotic prophylaxis for close contacts (for mother–neonatal pairs, contacts of severe iGAS disease cases, and in other special circumstances), informed by a literature review in the Appendix.6
National guidelines for iGAS are currently being developed and these need to include advice tailored for the vastly different epidemiology seen across Australia, reflecting a contrasting diversity of endemicity of GAS‐related disease. This has also been necessary for the Australian guidelines for diagnosing acute rheumatic fever, with low risk and high risk populations defined.7
Competing interests
No relevant disclosures.
References
- Gibney K, Steer A. Reducing the burden of group A streptococcal disease in the Northern Territory: the role of chemoprophylaxis for those at greatest risk. Med J Aust 2022; 217: 524‐525. https://www.mja.com.au/journal/2022/217/10/reducing‐burden‐group‐streptococcal‐disease‐northern‐territory‐role
- Birrell JM, Boyd R, Currie BJ, et al. Invasive group A streptococcal disease in the Northern Territory and the impact of melioidosis antibiotic prophylaxis. Med J Aust 2022; 217: 544‐545. https://www.mja.com.au/journal/2022/217/10/invasive‐group‐streptococcal‐disease‐northern‐territory‐and‐impact‐melioidosis
- Mearkle R, Saavedra‐Campos M, Lamagni T, et al. Household transmission of invasive group A Streptococcus infections in England: a population‐based study, 2009, 2011 to 2013. Euro Surveill 2017; 22: 30532.
- Davies HD, McGeer A, Schwartz B, et al. Invasive group A streptococcal infections in Ontario, Canada. Ontario Group A Streptococcal Study Group. N Engl J Med 1996; 335: 547‐554.
- Robinson KA, Rothrock G, Phan Q, et al. Risk for severe group A streptococcal disease among patients’ household contacts. Emerg Infect Dis 2003; 9: 443‐447.
- Merridew N, Birrell J; NT Health. Public health management of invasive group A streptococcal disease in the Northern Territory guideline [version 2.0, 18 May 2022]. https://health.nt.gov.au/__data/assets/pdf_file/0009/1111122/invasive‐group‐A‐streptococcal‐disease‐northern‐territory‐guidelines.pdf (viewed Dec 2022).
- RHDAustralia (ARF/RHD writing group). The 2020 Australian guideline for prevention, diagnosis and management of acute rheumatic fever and rheumatic heart disease (3.2 edition, March 2022). RHDAustralia, 2020. https://www.rhdaustralia.org.au/arf‐rhd‐guideline (viewed Dec 2022).