Diphtheria caused more deaths in Australia in the early 1900s than any other infectious disease. Thanks to diphtheria vaccines being rolled out nationally since 1932, it has almost disappeared, though it remains endemic in countries without organised vaccination programs.
It’s why two cases in young children being reported within two days, both in northern New South Wales, has caused alarm. An unvaccinated toddler is in intensive care with the disease. On Sunday the child’s six-year-old unvaccinated brother also tested positive, and is being treated in hospital as a precaution.
What is diphtheria?
Diphtheria is a contagious bacterial infection caused when the bacterias, Corynebacterium diphtheriae or Corynebacterium ulcerans, produce a toxin.
Infection with this toxin causes severe inflammation of membranes in the nose, throat, windpipe and heart. It can also cause nerve damage, life-threatening heart failure, and paralysis.
In many cases a membrane forms on the back of the throat comprised of cell and fluid waste and excretions. This can make breathing difficult and causes pain.
Dr Jane Frawley, a senior lecturer in public health at the University of Technology Sydney said: “It’s quick.”
“Within two days that membrane can start forming. The symptoms before then are often quite mild, so parents could very easily mistake it for a cold. Once the membrane forms, it’s potentially very dangerous.”
What is the latest on the children infected?
Dr Paul Douglas, the director of North Coast Public Health, told Guardian Australia that the two-year-old remains in intensive care.
“I am very confident in the treatment that child is receiving, that the doctors are managing this very well, and that the child will do well,” he said.
Research has found diphtheria can have a fatality rate of 5-10%, and that this reach 20% in children under five. However Douglas said: “That’s based on very old data because we just don’t see this disease any more.”
“Medicine has changed so much since that time,” he said. “We’ve got the anti-toxin therapy now, and antibiotics.”
Where did these two cases come from?
Most Australian cases of diphtheria come from overseas. In 2018, an unvaccinated man in his 20s who had never been overseas died from diphtheria myocarditis (inflammation of the heart muscle).
Douglas told Guardian Australia on Monday that in terms of the most recent two cases, “We now believe this is certainly something that’s developed locally”.
“The bacteria itself is endemic within our community,” he said.
“It’s a bit like tetanus, it’s always there. And if the right circumstances come along, then someone can get an infection. We think someone who is fully immunised began to colonise the bacteria either in a wound, or in their respiratory tract. And then they have come in contact with the unvaccinated children who are now infected.”
Who is at risk?
The risk of further spread is “almost zero”, Douglas said.
“My team have been fantastic and have now traced every single contact. Aside from the brother, they’ve all come back negative and we’ve given them all antibiotic treatment and also offered them all immunisation. So we strongly believe that we’ve curtailed the outbreak, but we will also continue to watch this closely for the next couple of days.”
Diphtheria spreads through close contact with infected individuals. It is usually spread from respiratory droplets after an infected person has coughed or sneezed.
Because most people have immunity, because the disease itself is rare and not as easily transmissible as other viruses, and because contact tracing has occurred, a wider outbreak is unlikely.
However Douglas is urging anyone who has never been vaccinated against diphtheria, anyone 50 and over who hasn’t received a booster, and anyone else eligible for a vaccine such as pregnant women to get up-to-date.
Is vaccine refusal a factor in the recent cases?
Data for the northern NSW region, where the two recent cases are from, show childhood vaccination rates are much lower in the region than elsewhere in the state. The latest data from 2021 shows 84.7% of children were fully immunised by age two in northern NSW compared to 91-96% of children in other regions.
Research into childhood immunisation in Northern NSW has consistently shown high rates of vaccine refusal. The research found some of these parents reported negative experiences with health professionals where they felt dismissed, that they feel concerned about too many health interventions, and that they seek health information from friends and family rather than health professionals or good scientific sources.
Douglas said “most” of the unvaccinated close contacts of the two infected children had agreed to get vaccinated over the weekend.
What’s being done to address low vaccination in the region?
Douglas said the pandemic had exacerbated issues with vaccination since people had not been seeing their GP as regularly, missing opportunities for vaccine conversations.
“We set up a group called the Immunisation North Coast Committee several months ago involving the local Primary Health Network, some local GPs, pharmacies, the hospital and community, family and child health nurses to come up with specific strategies about how we can start to work more effectively with some of the more vulnerable and hesitant groups,” Douglas said.
“We’ve worked with acute hospitals so that when people turn up to emergency departments and paediatric wards, it is used as an opportunity to discuss vaccines and bring children up-to-date.”
Frawley said Australia is often applauded for its high vaccination rates, but it takes ongoing work to keep vaccination programs strong.
“It’s been so long since we’ve had diphtheria in any appreciable number that we have a second generation of parents who have never seen the disease,” she said. “It can be hard to encourage people to get a vaccine against something they’ve never heard of. We need to keep educating people, including about how nasty this disease is and how safe the vaccine is.”