The spread of a flesh-eating ulcer in parts of Australia is being described as a "rapidly worsening epidemic" and, to make matters worse, researchers say they don't know exactly where it comes from or how it is transmitted.
Known as Buruli ulcer, the infectious disease initially appears as a small red lump that closely resembles a pimple or insect bite, Daniel O'Brien, deputy director of the department of infectious diseases at Barwon Health in Victoria told The Washington Post. If left untreated the lump can gradually enlarge and within weeks cause "severe destructive lesions of skin and soft tissue," he said. Anyone is susceptible to the disease, which usually infects a person's arms or legs, he said.
Compared to other types of flesh-eating bacteria, such as necrotizing fasciitis, Buruli ulcer is not the "most aggressive," but O'Brien said the disease can sometimes "eat away one limb or a large part of a limb." The ulcer can even affect bones, leading to permanent disfigurement and long-term disability, according to the World Health Organization. Severe cases often require extensive reconstructive surgery and lengthy recovery.
The disease most commonly occurs in central and West Africa, but it has recently reached "epidemic" levels in the Australia Victoria state, alarming researchers and prompting a call for an "urgent scientific response," according to an article published Monday in the Medical Journal of Australia. An epidemic is defined "by cases rapidly increasing in number, becoming more severe in nature and occurring in new geographic areas," the article said.
"Numbers are exploding," said O'Brien, who was the article's lead author.
In 2017, there were 275 reported cases in Victoria, a 51 percent increase from 2016, O'Brien said. Additionally, the number of cases classified as severe have doubled in the last five years, he said. Victoria is one of the country's most populous states, home to the city of Melbourne.
Last year, a 13-year-old girl from a town in Victoria contracted the disease on her knee and had to undergo three surgeries as well as months of "powerful antibiotics," the BBC reported.
She described the disease as progressing from a "swollen and inflamed" knee to seeing her skin break down, the BBC reported.
According to the article, about 2,000 cases are reported worldwide every year.
Buruli ulcer can be treated using a combination of antibiotic regimens, with cure rates approaching 100 percent, according to the article. However, most people do not even know they have been infected since it can take up to six months for symptoms to show, O'Brien said. The disease, which is from the same family as leprosy and tuberculosis, is caused by a bacteria known as Mycobacterium ulcerans, he said.
"It's a pretty clever, well-adapted organism," he said, noting that the bacteria also produces an agent that stops a person's immune system from functioning.
In countries such as the United States, where the disease is not common, it could also take a long time to diagnose since normal tests do not pick up the "specialized" bacteria, O'Brien said.
Buruli ulcer is classified by the World Health Organization as a "neglected tropical disease," meaning it does not receive "the attention and research that it really needs," he said.
"There needs to be research done to answer some very vital scientific questions," he said. "There are very significant knowledge gaps."
There are many mysteries surrounding the disease's rapid spread in Australia, especially since the number of reported cases around the world is decreasing, O'Brien said.
To start, Buruli ulcer is defined as a tropical disease, but the region of Victoria has a temperate climate, O'Brien said. Even though the disease was first recognized in Victoria in 1948, a majority of cases have since been found in areas such as Africa, South America and New Guinea, he said.
Scientists also do not know how people contract the disease or where it lives in the environment.
"It seems like something has obviously changed in the interactions between the environment, animals and humans," O'Brien said about the spike in cases in Victoria. "We have some theories and some clues, but we don't know the answer."
Most cases have been associated with wetlands, especially areas with slowing or stagnant waters, according to the article, which cites mosquito bites as a possible way to transmit the disease. But in Australia, O'Brien said people could be exposed to the bacteria through a variety of sources in the environment, for example the soil. Once it is on a person's body, he said the bacteria needs a way to get under the skin, which can happen through an insect bite, puncturing injury or preexisting wound.
People have a higher risk of getting the disease during warmer months, O'Brien said, adding that wearing less clothes increases chances of exposure.
Luckily, O'Brien said research has been done to indicate that the disease is not likely spread through contact with other infected people. Groups of people, such as families, who present symptoms are probably a result of being in the same environment, he said.
However, O'Brien said Australian scientists have not received enough funding to conduct "intensive, thorough" research into the disease.
"We've appreciated the money we've had, but it hasn't give us the answers," he said.
Without a solid understanding of Buruli ulcer, O'Brien said it is difficult to predict its spread and prevent it.
"The basic thing is that information is not known and that information is absolutely vital to controlling [the disease]," he said. "If people didn't work out how you caught it, how would you control it?"