Australia is confronting its most severe diphtheria outbreak in decades, with health authorities confirming more than 220 cases across four states since January and urging residents to ensure their vaccinations are current.
The Northern Territory has recorded 139 cases, Western Australia 82, South Australia seven and Queensland three, according to the latest figures released Thursday. The federal government has responded with a A$7.2 billion emergency support package aimed at increasing vaccination rates and bolstering health services in the affected regions.
Diphtheria, caused by toxin-producing Corynebacterium diphtheriae bacteria, spreads through respiratory droplets or contact with skin sores. There are two primary forms: respiratory diphtheria, which can damage the heart, nerves and airways and carries a mortality rate of up to 10 percent even with treatment, and the generally milder cutaneous version that produces skin ulcers.
Officials note that the majority of cases in the current outbreak are cutaneous, though roughly 30 percent involve the respiratory form. Approximately 94 percent of those affected since January 2026 are Aboriginal and Torres Strait Islander people, according to the Australian Centre for Disease Control.
Health experts point to several contributing factors, including waning immunity, lower routine immunisation rates and higher rates of skin infections in some communities. Overcrowding and limited access to health care are also believed to play roles in the spread.
"Vaccination is the best way to prevent severe diphtheria infections, and the further spread of the disease," health authorities have stated in recent advisories. Before widespread vaccine introduction in the 1950s, diphtheria claimed many lives annually, particularly among children.
Since vaccines became routine, deaths have become rare. Australian records show only four diphtheria-related fatalities between 1999 and 2025. The combined diphtheria, tetanus and pertussis vaccine, known as DTP, forms the cornerstone of protection.
Children in Australia receive the vaccine at two, four, six and 18 months, with additional doses at four years and in early adolescence. Adults are advised to obtain boosters every ten years, though new guidance for Aboriginal and Torres Strait Islander people and health-care workers in outbreak areas recommends doses every five years.
Pregnant women should receive a booster between 20 and 32 weeks of pregnancy to protect both themselves and their infants. Additional doses are offered to those with mild cases or close contacts of confirmed infections.
Even among vaccinated individuals, breakthrough cases have occurred. An estimated 90 percent of those diagnosed in the current outbreak had received prior vaccination, though most experienced only mild symptoms. Tragically, one person has died from the disease.
Both NT Health and WA Health have issued specific outbreak immunisation schedules for residents and workers in impacted communities. Public health departments continue to monitor the situation closely.
Residents in affected areas experiencing sore throats or skin sores are encouraged to visit local clinics promptly. Those with fever, breathing difficulties, swallowing problems or a greyish membrane in the throat should seek emergency care immediately.
The outbreak has highlighted the importance of maintaining high vaccination coverage, particularly as national childhood immunisation rates have fallen to a five-year low following the COVID-19 pandemic. Immunity from the DTP vaccine diminishes over time, leaving many middle-aged adults without adequate protection without boosters.
Local clinics, community health services and Aboriginal Medical Services stand ready to administer vaccines and provide guidance on individual schedules. Authorities continue to stress that timely vaccination remains the most effective tool against further spread.