By Liam Mannix
Nearly everything about Victoria’s flesh-eating ulcer outbreak is mysterious.
We don’t know how it got here. We don’t know how or why it’s spreading. We don’t know where it’s coming from.
And, most worryingly, we don’t know where it’s going next.
Here's what we do know.
Gus Charles and his mother Sally. Gus was diagnosed with a Buruli or Bairnsdale ulcer about 12 months ago.Credit: Mathew Lynn
What are Buruli ulcers? Do they really eat my flesh?
Buruli ulcers develop when a bacteria known as Mycobacterium ulcerans manages to get a foothold in the skin.
“It spreads quite slowly but progressively in the layer between skin and muscle. It’s quite silent for a while, you might not notice it,” says Professor Paul Johnson, director of research at Austin Health.
“It’s not as painful as you would think when you look at the pictures. We think that’s because it interferes with pain signals as well.”
The bug secretes a toxin, mycolactone, that slowly liquefies tissue. The toxin also turns off the immune system, so your body cannot fight the infection.
The ulcer itself is a big lump of tissue that has either been liquefied by the bacteria or rotted away, leaving a deep abscess. Ulcers typically look like hardened lumps from the outside; patients are often horrified by how much damage has been done below.
Luckily, treatment – typically long-term antibiotics – is very successful, especially if the disease is caught early.
How do I know if I have one?
Buruli ulcers start as non-healing sores, usually on the leg or arm. Over time, they slowly get bigger and bigger. There are few other symptoms, part of the reason early diagnosis is so difficult. If you think you have one, see a doctor.
What’s causing the outbreak? How is it spreading?
No one knows. Scientists are urgently scrambling to find out.
The leading candidates: possums and mosquitos.
It's theorised the possums are the real targets of Ulcerans, and humans are just collateral damage. Professor Johnson thinks the disease might spread through possums and other animals, and then be transmitted from possums to humans via mosquito bite.
“But we don’t know why they get it, or where they get it from, or why it moves through them and then leaves.”
The fact that most infections occur on the upper arm and calves, where flesh is exposed, also suggest a link.
But we cannot prove this either. Other studies suggest the bacteria gets on the skin from other sources, maybe infected dirt or water, and then a mosquito bite opens up a small hole, allowing the infection to start.
I heard there's an epidemic?
After bubbling away in Gippsland for more than 70 years, the disease has been on a path of rapid expansion since the early 2000s.
It hit the national spotlight last year, with doctors now describing the situation in some areas – particularly the Mornington Peninsula, around Rye – as an epidemic. (See the graph above.)
Where am I likely to get one?
Mycobacterium ulcerans is already endemic in several parts of Victoria – and it seems to be spreading. Australia is the only developed country with an outbreak in the world; most of the other cases are in sub-Saharan Africa.
At the moment, the places you’re most at risk are on the Mornington Peninsula. Infections are concentrated around Rye, Blairgowrie and Tootgarook, but scientists are starting to see cases occur far north of there in Melbourne’s outer suburbs. See the map (above) for the disease’s geographical spread.
Disease outbreaks seem to be linked to wetlands, and occur in hotspots – some areas are endemic, but others only a few kilometres away have almost no incidence.
How can I cut the risk?
Here are Professor Johnson’s top tips when visiting high-risk areas:
- Avoid mosquito bites: wear shoes, long sleeves and trousers and apply repellent.
- Wash and cover wounds sustained outside while working, playing or gardening.
- See your doctor if you are concerned.