Diphtheria is back in the Australian headlines, with four cases of the potentially deadly respiratory type and 16 of the cutaneous type.
Queensland has recorded 18 cases of diphtheria in the first six months of this year, with all but two of them confirmed as cutaneous diphtheria.
The news has prompted a warning from infectious diseases and immunisation expert, Professor Robert Booy, for clinicians to be on alert for the highly transmissible disease.
“It’s important to pay attention to public health [alerts] and make sure that everyone is up to date on the latest information, and of course vaccination is key,” he said.
Diphtheria is back in the Australian headlines after weekend reports of two new cases of respiratory diphtheria in northern NSW siblings aged two and six.
The North Coast Public Health Unit has confirmed the two children are in hospital, one in ICU and one under observation. Both children were unvaccinated.
The children’s close contacts have received post-exposure prophylaxis, which can include antibiotics and immunisation, to reduce the risk of transmission.
A spokesperson for Queensland Health provided a statement to The Medical Republic this week confirming that 16 of the state’s cases were cutaneous diphtheria and two were respiratory diphtheria.
“The majority of Queensland’s cases are vaccinated and, as a result, have not experienced life-threatening illness,” the statement said.
“Due to improvements in laboratory testing techniques, we are seeing increases in cases of this less transmissible type of diphtheria, which previously might not have been identified.”
These are the first cases of respiratory diphtheria seen in Australia since the 1990s. Figures from the Communicable Diseases Network Australia’s fortnightly report show the rolling five-year mean for diphtheria cases in Australia is 1.4.
With 20 confirmed cases so far this year smashing that average, health experts are watching the trend closely.
And while cutaneous diphtheria is a far less serious disease – causing skin rashes and lesions that can look like ulcers with a definite edge – it is still notifiable, said Professor Booy, of the University of Sydney’s National Centre for Immunisation and Surveillance.
“The cutaneous form is very transmissible, and it’s very easily spread,” he said.
“It’s unlikely to cause heart complications, but it’s definitely worth paying attention to, ensuring that people are getting better and ensuring that they’ve been vaccinated and they’re isolating and not transmitting the infection to any other children.”
A spokesperson for the federal Department of Health and Aged Care said cutaneous diphtheria was caused when bacteria infected a wound or lesion in the skin and could cause small skin sores that formed larger ulcers, commonly on the legs.
“Cutaneous diphtheria is commonly associated with tropical climates, and cases reported in Australia are often associated with overseas travel,” the spokesperson said.
“Recent increases in reported cases beyond the quarterly and yearly rolling five-year mean respectively may be in part due to increased travel and mobility as covid-19 restrictions have relaxed in more recent times.”
Professor Booy said that while the rash and the lesions were not typically very painful, it was important to confirm the diagnosis if there was a suspicion of diphtheria and make the appropriate notifications to health authorities.
And he warned that just two confirmed cases of respiratory diphtheria could be enough to spark a local outbreak.
“We’ve already seen transmission once already. I don’t think there would be a state-wide or national outbreak because vaccination rates are so high,” he said.
“The whole point of vaccination is that you get widespread immunity, which stops spread transmission. We’ve stopped the disease in its tracks, so the herd immunity is likely to be operating.
“But the likelihood in a local community with a high proportion of children unvaccinated, who may go to a day care centre where there’s crowding – those certainly are risk factors for local transmission.”
Like its skin version, respiratory diphtheria is a contagious, vaccine-preventable disease. It is spread mainly through respiratory droplets during close contact with a person who has the bacteria.
Dr Paul Douglas, director of NSW North Coast Public Health, said the risk to the broader community was low.
“However, this is a very serious disease and can be fatal, so families should be alert and review the immunisation status of their children on the Australian Immunisation Register or with their medical provider, to ensure they are update with all vaccinations,” Dr Douglas said.
“Diphtheria is very rare in Australia due to our longstanding childhood immunisation program. The diphtheria vaccination is free and readily available from your GP for everyone from six weeks of age. It is important that everyone keeps up to date with their vaccinations.”
Immunisation protects against severe diphtheria and is included in the Australian Childhood Immunisation program. In Australia, children are vaccinated at six weeks, four months, six months, 18 months, four years and at the beginning of high school.
In adulthood, diphtheria vaccine is included with tetanus and pertussis vaccines in the DTPa vaccines, which are recommended for adults every 10 years and in pregnancy.
