Understanding risk factors is key to defining the source and transmission route of Mycobacterium ulcerans 
 
 Mycobacterium ulcerans causes an infectious disease known internationally as Buruli ulcer, and also as Bairnsdale ulcer or Daintree ulcer in Australia.
– "It is difficult to prevent a disease when it is not known how infection is acquired," reads a study published Monday that tracks the spread of a flesh-eating ulcer in Australia, and that's not the only mystery surrounding the rise in Buruli ulcers. The disease has historically most often struck in tropical and swampy parts of Africa, but incidents of it have surged in Victoria, which the BBC notes has a "temperate" climate—and only Victoria, with no cases reported in the neighboring Australian states of New South Wales, South Australia, and Tasmania. The ulcers were first reported in Victoria 70 years ago, but the surge is a recent one: 182 new cases in 2016, a 72% rise over the previous high; and though total 2017 figures weren't in, the year was shaping up to show 50% more cases than in 2016. Buruli expert Paul Johnson, who was not involved in the study, notes the oddities about how the disease appears in Victoria, telling the Guardian, "If you don’t enter an endemic area, you don’t get the disease." But "when you enter an endemic area, it looks the same as the area you just left." He suspects the bacteria that causes the ulcer is carried by mosquitoes and possums. The bacteria produces toxins that eat through fat, skin cells, and blood vessels in the fatty layer of the skin; it's only once the ulcer erupts through the skin's outer layer that a person becomes aware they are infected. The study, which appears in the Medical Journal of Australia, argues government funding needs to quickly be dedicated to studying the ulcer in order to answer six critical questions, including "why are cases becoming more severe?" (The bacteria gave this girl a "zombie leg.")