In Southeast Asia, Cambodia has a well-earned reputation as a leader in the fight against the virus.
Government action and large funding from donors have seen Cambodia's HIV infection rate drop by almost two thirds, over the past 15 years.
Now, there are concerns that this success may be jeopardised by heavy handed policing and a fall in donor funding.
Reporter: Robert Carmichael
Speakers: Dr Mean Chhivun, head of The National Centre for HIV/AIDS, Dermatology and STD (NCHADS); Marie-Odile Emond, country director of UNAIDS
CARMICHAEL: Over the past 15 years, Cambodia has become something of a poster-child in the battle against HIV, and in that it has been helped by plenty of donor money: the bulk of the 50 million dollars the country spent tackling HIV in 2012, for example, came from donors such as the Global Fund, the U.S. government and the Australian government.
All those millions have allowed the Cambodian government to target high-risk groups, to put in place a well-regarded prevention program, and to ensure those who need treatment receive it.
That has helped to cut the rate of HIV infection in the adult population to 0.7 percent. Cambodia did so well that it met its 2015 Millennium Development Goal of 1 percent infection five years ahead of schedule.
But the battle against HIV/AIDS - which in Cambodia is transmitted largely through heterosexual sex - isn't yet won, and a combination of issues could see some of those gains lost.
EMOND: "My name is Marie-Odile Emond. I'm the UNAIDS country director for Cambodia."
CARMICHAEL: UNAIDS' Emond highlights some of Cambodia's key achievements: 83 percent of the 76,000 HIV-positive citizens get antiretroviral drugs, for instance - one of the highest rates of any low-income country. In addition, HIV education is being introduced into the secondary school curriculum to teach the next generation of its dangers.
But with a low HIV prevalence, and with just 1,000 infections a year in the 15-million-strong population, it's becoming harder to find the newly infected. So UNAIDS and others are retargeting their efforts to locate people who are slipping through the net.
They also need to do better reaching high-risk, marginalized groups such as sex workers, injecting-drug users, men who have sex with men, transgender people, prison inmates and migrants.
That's where it gets tricky, thanks in part to two controversial pieces of legislation - a 2008 law to combat human trafficking and another to improve security in communes and villages. The human trafficking law outlawed brothels and drove much sex work underground.
EMOND: "And the impact of those laws has been really to lead a lot of those populations who are, you know, at risk for HIV - sex workers or drug users - to be afraid of being arrested and to then operate in a more hidden way. You know, every day we hear issues of people not accessing services or being denied services or being really harassed or detained for a few days, abused also - and that's a very serious concern from a public health perspective for the HIV epidemic, because this really could undermine the last steps that Cambodia needs to do to reach the elimination of new infection."
CARMICHAEL: Emond also hopes the Cambodian government will increase the money it puts into combating HIV to compensate for announced cuts in donor funding - the Global Fund, for instance, has effectively halved its funding to Cambodia. All of this, she adds, means the country is "coming to a crossroads".
The drop in funding has already hurt half of the 120 NGOs and civil society groups that belong to the HIV/AIDS Coordinating Committee, or HACC, an umbrella group. That has affected programs and outreach work to at-risk groups, such as sex workers, of whom around 14 percent are HIV-positive. HACC says mother-to-child transmission remains a problem too - its prevalence is around 8 percent.
HACC says these pockets of high prevalence must be addressed, but that effort won't be helped if, for instance - as happened most recently in June - Cambodia's courts allow the presence of condoms as evidence of prostitution. Not surprisingly, some owners of beer gardens and karaoke bars won't allow condoms on their premises for fear they will be accused of operating a brothel.
Dr Mean Chhivun is the person tasked with combating HIV/AIDS, which he does from the offices of the National Centre for HIV/AIDS, Dermatology and STDs, known as NCHADS. Dr Chhivun has run NCHADS, which is part of the Ministry of Health, since 1998.
Although he wouldn't be drawn into criticising the actions of other government departments, he admits that reaching key groups was easier prior to the passage of the anti-trafficking law.
Despite the challenges, he is confident that the structure of the program he has helped build will help. NCHADS and its partners already work with groups representing the most marginalized, such as sex workers, and it has undertaken other low-cost steps too. A year ago, for example, it introduced finger-prick testing for HIV. That now reaches 40 percent of those in the highest risk groups, he says, and should reach 90 percent within a year.
MEAN CHHIVUN: "So based on the experience we have in the past 15 years, based on the lessons we learned to fight against HIV and to provide better care to people who are living with HIV and AIDS, we set up a very ambitious goal to eliminate new HIV infection by 2020."
CARMICHAEL: The funding cuts, he says, simply mean doing more with less.
MEAN CHHIVUN: "We have to identify the low-cost intervention but with high impact or good result. This is very important because we use our capacity that already built in the past 15 years to maintain our effort and also to maintain the coverage - this is the main challenge that we are facing in the future for the financial gap."
CARMICHAEL: As Cambodia looks ahead to its ambitious 2020 goal of zero HIV infections, it will have to do a better job reaching out to marginalized groups. But logic dictates it will be harder for the Ministry of Health to succeed unless the police and the courts stop targeting high-risk groups for prosecution and abuse.