Nestled among the bars and strip clubs of Sydney's Kings Cross is a service which not only saves lives, but continues the pragmatic approach which prevented a HIV epidemic among drug-users in Australia.

Behind a nondescript shopfront is the Sydney Medically Supervised Injecting Centre -- the only place in the southern hemisphere where users can inject heroin and other drugs under the care of registered nurses.

Those who use the injecting room -- typically people who have taken drugs for more than a decade -- are given a plastic spoon, a tourniquet and a clean syringe as well as a stainless steel cubicle in which to inject.

"We know the evidence behind needle syringe programmes and the benefits they have in terms of prevention," says the centre's medical director Marianne Jauncey.

"In Australia, for instance, they have very clearly prevented an epidemic of HIV among people who inject drugs. And they are important in ongoing prevention for hepatitis C."

Global AIDS-related deaths and new HIV infections have fallen by over a third in a decade, according to figures released by the United Nations before this week's 20th International AIDS Conference in Melbourne.

But concerns are mounting that vulnerable and marginalised groups could miss out on treatment and education, with the situation particularly serious among people who inject drugs in south-west Asia and eastern Europe.

Needle and syringe programmes are seen as among the most important harm reduction services for avoiding HIV infection, and in Australia where these are widely available transmission of the virus among drug users is low.

Australia recorded 1,236 new cases of HIV infection in 2013, meaning infections remain at a 20-year high, but experts say transmission is more commonly through unsafe sex.

"Australia is lauded for its efforts in preventing an epidemic of HIV, specifically among people who inject drugs," Jauncey says.

"As a doctor who works in drugs and alcohol, I'm not an expert in HIV, I don't have to be because we've prevented this epidemic amongst the people I see."

- No deaths since opening -

Jauncey remembers the days before Australia opened its first, and so far only, medically supervised injecting centre in Kings Cross in 2001 -- drug use was common, needles littered the streets and overdoses were all too regular.

"It was expected up and down the streets of Kings Cross," she said, explaining that in the 1990s, heroin was cheap and widely available in Australia, and more young people were using and dying.

While clean needles had been available for years, the centre was the first place where users could legally take drugs under medical supervision; avoiding the possibility of an accidental overdose.

The first such centre was opened in Switzerland in 1986 and dozens more have followed, but the Sydney operation was the first in the English speaking world and remains the only one in the southern hemisphere.

Since it opened, its staff have dealt with 4,937 overdoses but like at the other 90-plus medically supervised injecting centres around the world, none have resulted in a death, says Jauncey.

"If this service wasn't here we would go back to those days of seeing a lot more issues with drug use in public," she adds.

Jauncey also cites the success of the centre in simply engaging with its clients, who are often homeless, or suffering from mental illness, and of helping them with other health services, including rehab.

"Anything we can do to start the conversation is a good thing. This is about making contact with marginalised people," she says.

Tony Trimingham's 23-year-old son Damien died 18 years ago from a heroin overdose, in a deserted stairwell not far from the Kings Cross service.

He'll never know whether the centre could have kept his son alive, but he says families are generally supportive of harm-minimising strategies such as medically supervised injecting rooms.

"What we know for sure is that this centre has saved lives, no question about that," he says.