A person has been diagnosed with leprosy in the Northern Territory - the fifth case reported in Australia so far this year.

It is the first confirmed case of the relatively rare but curable disease in the NT since 2021, the NT Health Department said on Thursday.

"Since the 1970s, leprosy case numbers have dramatically decreased, with less than one case confirmed per year on average since 2000 in the NT," a spokesman said.

The case was recorded in northeast Arnhem Land, about 1000 kilometres east of Darwin.

There have been three reported cases in NSW and one in Victoria so far this year, according to federal government health statistics.

Last year there were eight cases reported nationally, with three each in Queensland and Victoria and two in NSW.

Leprosy is an ancient and chronic disease caused by the bacteria, Mycobacterium leprae, and often affects the nerves of the hands, feet and face.

The disease is transmitted through droplets from the nose and mouth but prolonged, close contact over months with someone with untreated leprosy is needed to catch it.

There is often much fear and misunderstanding about leprosy because it can cause disabilities, but it is not very contagious and easily treatable with antibiotics, the department said.

According to the World Health Organisation, leprosy cases continue to be diagnosed in more than 120 countries, with more than 200,000 new cases reported every year.