The surprise discovery of flesh-eating ulcers hundreds of kilometres from existing case clusters has sparked concerns it has become entrenched in another state.
Buruli ulcer has been known to occur in Australia since the 1940s with cases noted in the Northern Territory and Queensland's far north.
Researchers are intrigued by a surge in Victoria, where a case is reported nearly every day, and its emergence in a southern NSW coastal town.
Recently published analysis suggests it has become endemic in the NSW town of Batemans Bay, about 110km southeast of Canberra.
Researchers pored over the coastal town's two known cases, reported in 2021 and 2023, as well as picking apart 27 samples of possum poo.
Possums are thought to be the main reservoir of the ulcer-causing bacteria, while mosquitoes act as an significant transmitter to humans.
"The new cases we report here in Batemans Bay could be a harbinger of a disease expansion in NSW similar to Victoria," the group of Australian researchers said in peer-reviewed journal PLOS Neglected Tropical Diseases.
"The detection of positive possum excreta samples from Batemans Bay establishes beyond doubt that (the bacteria) is present in local possums."
The bacteria found in the NSW coastal town was distinct from the lineage prevalent in the most endemic areas of Victoria, including Melbourne, Geelong and surrounds.
The discovery of Buruli ulcer in Batemans Bay had generated significant interest from local and interstate authorities, the research's lead author and infectious disease physician Mehrab Hossain said.
"We were surprised to find Buruli ulcer in Batemans Bay, as there had been no previous cases reported in the region," she told AAP.
More research might be needed in other parts of southeast Australia as additional cases arise, she said.
The community shouldn't panic, however.
"These infections are highly treatable, (but) it's important to remain vigilant," Dr Hossain said.
The lesion typically takes weeks or months to ulcerate after appearing as an insect bite, making early recognition and diagnosis critical to preventing skin and tissue loss.
In one of the Batemans Bay cases, a 94-year-old man's ring finger was amputated after a large skin lesion with the ulcer-causing bacteria spread.
"If you notice a skin infection that isn't healing despite antibiotics, it may require further investigation, including testing for Buruli ulcer," Dr Hossain said.
"Additionally, preventing mosquito bites by using insect repellents and other protective measures is an effective way to reduce the risk of infection."
Researchers said the many similarities in wildlife composition and insect presence between coastal Victoria and southern NSW made it likely NSW health authorities face progressive expansion of ulcer-endemic areas.
Questions remain as to why cases in humans are popping up in areas sometimes hundreds of kilometres apart.
