"I started feeling pain in my knee in early April. Slowly it got worse, with my knee becoming swollen and inflamed, until one day, the skin started breaking down," an Australian teen, Ella Crofts said in a change.org petition.

Bacteria are eating up her leg and the bacteria usually found in tropical countries is on the increase in Australia.

The flesh-eating bacteria have left health authorities puzzled and concerned.

The Victorian Health Department said on Thursday that cases of mycobacterium ulcerans, which caused flesh-eating ulcers known as Buruli ulcers, had already increased 50% since in 2016.

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A health department spokesman said the state had already seen 159 cases this year, compared to 102 cases in 2016.

“It is an increase, but for reasons we fully don’t know why. It’s a medical conundrum,” he told the Australian Associated Press.

Experts from a public health laboratory were investigating the bacteria.

“The infection starts as an insect bite, causing swelling and grows into large lesions requiring major surgery. The bacteria is usually found in tropical countries,” the health department spokesman added.

Ella Crofts, who has experience the flesh-eating bacteria required 3 operations to repair the damage.

“Why are the numbers in Victoria increasing so rapidly?” Croft asks in the petition that has already garnered more than 9,000 signatures.

Geelong Hospital’s deputy director of infectious diseases, Daniel O’Brien, called it an “epidemic”.

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“It is getting more severe. We see now twice as many severe cases as we saw 4 years ago. And the biggest concern is we don’t know how to prevent it,” he told local Fairfax media on Thursday.

It is not, however, ascertained if the bacteria can be transmitted.