Australia is battling its largest diphtheria outbreak in living memory

Diphtheria is surging in Australia for the first time since widespread vaccination began in the 1930s.

The country has recorded 230 cases of the dangerous bacterial infection and one related adult death this year, with case numbers accelerating. The majority have occurred in Indigenous communities in remote areas of the Northern Territory and Western Australia, with smaller numbers in Queensland and South Australia. Previously, the number of cases per year was typically zero or close to zero.

The chief health officer of the Northern Territory, Paul Burgess, told the Australian Broadcasting Corporation (ABC) that the outbreak appears to have started with a case in Queensland in 2022 that was acquired overseas. Since then, the highly infectious disease has crossed the border into the Northern Territory and spread among Indigenous communities there and in other states, most likely due to gaps in vaccination, high levels of movement between the communities and crowded housing conditions, he said.

Almost 92 per cent of 5-year-olds are vaccinated against diphtheria in the Northern Territory, but no more than 67 per cent of 13-year-olds are receiving the recommended booster offered nationally through school-based programmes. “The vaccine does wane, and boosters are needed,” says Raina MacIntyre at the University of New South Wales.

This may explain why many adolescents and young adults are becoming infected with the disease.

One contributing factor to sub-optimal vaccination rates is “the rise in vaccine misinformation and pushback against vaccines after the Covid-19 pandemic”, says MacIntyre. Shortages of nurses and doctors in these remote areas may be another factor.

Diphtheria is caused by Corynebacterium diphtheriae bacteria, which infect the skin or respiratory tract and produce diphtheria toxin. Infections cause ulcers on the skin or the formation of a thick grey membrane in the throat, making it sore and obstructing breathing. If the toxin gets into the bloodstream, it can lead to heart failure or paralysis.

The bacteria can be picked up through contact with an infected person’s ulcers or by breathing in their respiratory droplets.

Treatments include antibiotics and an antitoxin that neutralises the diphtheria toxin, but some people die even with these interventions.

Before the diphtheria vaccine became available, the disease was a common cause of child deaths globally. In Australia, more than 4000 people died from diphtheria in the late 1920s and early 30s.

The Australian government has just announced A$7.2 million (£3.8 million) in funding to try to contain the outbreak, and extra doctors and nurses are being deployed to affected areas to administer booster vaccines and treatments.

“Quite pleasingly, we’re seeing quite a strong community demand currently for vaccination in the context of this outbreak,” Burgess told the ABC.

Globally, the largest outbreak of diphtheria since the advent of routine infant vaccinations occurred in the former Soviet Union states after the bloc dissolved in 1991. Over 140,000 cases and 5000 deaths resulted from the collapse of vaccination rollouts, revealing that “large diphtheria epidemics can occur when vaccination programmes get disrupted”, says MacIntyre.