Because of high vaccination rates, the Northern Territory of Australia had not seen locally transmitted toxigenic since the 1990s, until cutaneous diphtheria cases emerged in May 2025 and respiratory cases in March 2026. By 30 April 2026, there had been 131 cases (34 respiratory, 97 cutaneous) in an ongoing outbreak characterised by a high proportion of cutaneous cases with transmission driven by crowding and consequent poor skin health. Most patients have had mild disease due to prior vaccination.