The third edition of Tropical Infectious Diseases describes Mycobacterium ulcerans infection – otherwise known as the Buruli ulcer – as a “necrotizing infection of the skin, subcutaneous tissue, and bone”. If this flesh-eating microbe doesn’t sound at all pleasant, then you’d be right, which is why medical professionals are worried about a new, unexplained outbreak in part of Australia.
Writing in the Medical Journal of Australia, a team led by Barwon Health explains how the infection is normally found in the tropical regions of West or Central Africa. Every year, around 2,000 new cases of the disease are diagnosed, which affects all age groups and can lead to long-term disability, cosmetic deformity, and severe emotional and psychological trauma.
Once it infects its host, M. ulcerans – belonging to the same genus as leprosy and tuberculosis – produces a unique toxin which both causes tissue damage and inhibits the immune system’s ability to deal with it. Although it can be treated with powerful (side-effect prone) antibiotics, particularly damaging infections can require reparative plastic surgery.
Recently, however, the authors explain that there’s been a “worsening epidemic, defined by cases rapidly increasing in number” in southeastern Victoria, a temperate part of the country. In 2016, there were 182 new cases, the highest ever reported. In 2017, up to mid-November, there were a further 236 cases.
Although the disease has been acknowledged to exist in the state since 1948, very little progress has been made in curtailing the bacterium simply because we actually know very little about it.
The team emphasizes that “efforts to control the disease have been severely hampered because the environmental reservoir and mode of transmission to humans remain unknown.” This uncertainty is epitomized by the World Health Organization (WHO), which notes that the type of people that are infected, and the fact the disease specifically manifests itself in a case-by-case way, “[varies] considerably within and across different countries and settings.”
It’s entirely unclear how the infection is acquired. Several hypotheses have been bandied about, including several focused on certain soil conditions. Human-to-human transmission routes have also been suggested, but recent evidence, however, suggests that this doesn’t occur, even though cases are commonly clustered among families.
This new outbreak simply brings up more questions without providing any answers.
As ever, the incidence of the disease is highly focal, meaning that it only seems to occur in clearly defined areas. In other parts of the world, the infection generally occurs in areas featuring stagnant water, but these cases seem almost entirely localized to the Bellarine and Mornington peninsulas, which are coastal.
It’s unknown why case numbers are rising in the latter and falling in the former, despite their proximity. Cases are also “becoming more severe in nature” over time.
This current scenario reads like an epidemiologist’s worst nightmare: “As a community, we are facing a rapidly worsening epidemic of a severe disease without knowing how to prevent it,” the authors state. Lest we forget, it's already a major health problem in West Africa.
That’s why this report acts as a clarion call for further research on the subject. Describing the dearth of understanding as an “information void”, the team asks for local, regional, and national governments to “urgently commit” to funding a comprehensive research endeavor that can be used to comprehend and stop this outbreak before it spirals out of control.