Children as young as 12 are testing positive for syphilis in an outbreak of the disease affecting young Indigenous people in the Northern Territory, new data has revealed.

The NT's Centre for Disease Control (CDC) said there had been 134 reported cases of the sexually transmitted disease in the Central Australia, Barkly and Katherine regions since July last year.

That is up from 15 reported cases in the 2013-14 financial year.

The majority of the notified cases are in Indigenous people aged 15 to 19.

CDC spokesman Dr Matthew Thalanany said before the outbreak, the disease was at low levels across the Territory.

"For quite a few years it was on the decline in the Northern Territory and we were really pleased it was on its way out," Dr Thalanany told 783 ABC Alice Springs.

"But suddenly in July last year we noticed a more-than-expected number of cases."

Dr Thalanany said it was important doctors tried to determine the sexual partners of anyone that tested positive for the disease.

"It's a very delicate matter, it's difficult, but it is necessary," Dr Thalanany said.

"It's necessary we get to know who all the contacts are and we get to test them."

The disease can also spread from mother to unborn baby, potentially causing severe health problems for the child and even death.

Three babies tested positive in the past financial year.

Knowingly spreading the disease 'a crime', Health Minister says

NT Health Minister John Elferink said the outbreak was "disappointing", but vowed his Government was doing everything possible to tackle the problem.

"We do what we can possibly do, but unfortunately we cannot police people's bedrooms," Mr Elferink said.

"What we do do, of course, is education programs ... [and] provide treatment."

He said some people could be breaking the law in spreading the disease.

"Any child under the age of consent who develops a sexually transmitted disease is subject to an investigation and prosecutions are launched when we identify the people who rape children," Mr Elferink said.

"If a person knowingly spreads a sexually transmitted disease then they are also committing a crime."