Clinician alert: toxigenic diphtheria cases across North Queensland are on the rise

To the Editor: Until recently, detection of locally acquired tox gene carrying diphtheria in Australia was rare. Toxigenic diphtheria had almost disappeared from the Australian landscape, with the widespread uptake of the diphtheria toxoid vaccine. Diphtheria is predominantly caused by toxigenic Corynebacterium diphtheriae and can present as both respiratory and cutaneous diphtheria disease. There have been increasing reports internationally of diphtheria outbreaks primarily in vulnerable migrant populations.1 In Australia, there were 46 diphtheria cases between 1999 and 2019 (eight respiratory diphtheria and 38 cutaneous), with C. diphtheriae accounting for 87% of these cases.2 Since 2020, a genomically linked clone of tox gene carrying diphtheria bacteria has spread across North Queensland. Cases described here are from the Queensland Health's Notifiable Conditions Register. The Townsville Hospital and Health Service Human Research and Ethics Committee provided an ethics exemption (EX/2022/HREC/88895) for this study.