The bacteria known as Mycobacterium ulcerans causes a disease that leads to a severe, nasty flesh-eating ulcer called a Buruli ulcer that can cause permanent disability and deformity. (For the curious, the study authors include some vivid examples of how these ulcers eat away at skin and soft tissue. But fair warning: The pictures are extremely graphic.)

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So what do we know about this flesh-eating pathogen? For one thing, it’s usually more common in tropical areas in West and Central Africa, raising concerns about why the cases are suddenly cropping up with increasing frequency in Australia, particularly in the Victoria region. It can afflict adults, children, and animals alike.

“In 2016, there were 182 new cases [in this area]—the highest ever reported by 72%,” wrote the study’s authors. That number may rise yet again given the current pace of new case reports. And there are some pretty major roadblocks to fighting that spread. “Despite being recognized in Victoria since 1948, efforts to control the disease have been severely hampered because the environmental reservoir and mode of transmission to humans remain unknown,” said the researchers, adding that it’s “difficult to prevent a disease when it is not known how infection is acquired.”

What we do know is that the bacteria is associated with wet, tropical areas, and may possibly be spread by mosquitoes. It also seems to be more prevalent during warmer months and exposed areas of the skin are more susceptible to the gruesome lesions.

But the researchers list out six critical questions about Mycobacterium ulcerans, including: How is it transmitted; what role animals and the environment play in its spread; and why the cases appear to be getting more severe in certain parts of Australia.