Asia has made progress in containing HIV but must remove the stigma associated with the virus to fully consolidate the gains and keep it under control, international research chiefs say.
Speaking ahead of an international conference of 5,000 HIV/AIDS researchers in Sydney next week, America's top expert Anthony Fauci and his Australian counterpart David Cooper said HIV remained a major public health risk in Asia.
Fauci said predictions HIV would devastate Asia as it had Africa had proved false after local health authorities, which were initially slow to heed warnings, adopted pro-active policies.
But he said the potential for an epidemic still existed in a region estimated to have eight million people with HIV, a figure aid agency USAID says could climb to 40 million by 2010.
"The population density in Asia is so great, with countries like India and China that have a billion people each, that infection rates just have to track up a few percentage points and you're potentially looking at a catastrophe," Fauci told AFP.
Cooper, the co-chair of the International AIDS Society (IAS) conference, said responding to HIV was complicated by the fact that many suffers existed on the fringe of Asian society and faced discrimination.
"We're not going to have the generalised epidemics in our region that we've got in sub-Saharan Africa, we're going to have explosive smaller epidemics," he said.
"They tend to occur among drug users, also among gay men, sex workers or mobile workers such as truck drivers, fishermen who are more likely to pay for sex.
"In Asia, they're stigmatised and discriminated populations. The trick is to get into these vulnerable populations and provide non-judgemental healthcare."
Cooper cited China as an example of a country that had overcome its initial denial of an HIV problem but could go further if discrimination ended.
"China is responding pretty well, their reponse has changed, they're putting treatment in place and doing research," he said.
"But people are still very much concerned about the human rights issues and how people with HIV are treated in Chinese society."
China estimated last year that it had 650,000 HIV cases, although UN officials estimate the actual number is now higher.
A recent paper in British medical journal The Lancet praised China's adoption of schemes such as needle exchanges and awareness campaigns among gay men, although the UN said there was still resistance to confronting the problem at a local level.
In India, where the estimated number of HIV cases was this month halved to 2.5 million, the government has set out to target the type of at-risk groups identified by Cooper.
"They're talking about upscaling programmes with marginalised groups," said Anjali Gopalan, head of the Naz Foundation, which works primarily with men.
"There was quite a bit of silence on them earlier."
Indians with HIV are still often treated as social outcasts, with reports of doctors shunning AIDS patients and HIV-positive children being barred from attending school with other pupils.
In Cambodia, one of the countries hit hardest by HIV/AIDS, the authorities are concerned that discrimination is helping the virus spread.
"It is difficult for us since stigma causes infected people not to speak out and this quietly spreads the infection," said Ly Peng Sun, deputy director of the National Centre for HIV/AIDS and Dermatology.
"Bias can prevent us from fighting the virus successfully."
Vietnam has introduced laws banning discrimination against people with HIV, although locals say it means some employers simply find a pretext to sack infected workers, rather than admitting it is because of their illness.
"If this new law is effectively implemented, it will serve not only as a shield for the fundamental rights of people living with HIV... but also as a positive tool for fighting stigma and discrimination," UNAIDS Vietnam director Eammon Murphy said.
Thailand has adopted a different tack to breaking down the taboos regarding HIV with innovative education campaigns such as traffic police handing out condoms, an initiative dubbed "Cops and Rubbers."
The country, which has experienced about half a million AIDS deaths and has about the same number of HIV cases, has slashed infection rates since it appointed a cabinet-level anti-AIDS coordinator to oversee prevention efforts.
It is also pushing international drugmakers over access to generic versions of newer and more expensive HIV medications that are needed to treat patients who have become resistant to the old drugs.