The UNAids report says the progress can be attributed to huge increases in government spending, wider access to drugs and greater public awareness. But it warns against complacency and urges countries to continue concerted efforts not only to reduce rates of new infections even further, but also to address long-term impacts effectively, especially the economic and social consequences for societies having to cope with large numbers of people with Aids.

The problem is very serious in those lower-income countries, because the cost to their public-health systems caring for these people properly is very high.

Last year, the world set aside US$8.3 billion (Bt316 billion) to combat Aids. But that was not nearly enough to implement effective preventive measures and care for people with Aids in the lower-income countries, where most of them are left to die for lack of access to anti-retroviral drugs that would otherwise enable them to lead virtually normal lives for many years to come. UNAids estimates the cost to the world of fighting the epidemic effectively could reach $22 billion annually by 2008.

In Asia, Thailand and Cambodia are lauded as countries that have succeeded in lowering the incidence of Aids. However, Aids is spreading more rapidly in China, Indonesia and Vietnam. But because UNAids relies on national statistics compiled by individual governments, there is a possibility of wide discrepancies between reported Aids prevalence and the actual figures, particularly in countries whose governments tend to cover up bad news and where there is a lack of media freedom.

By the end of last year, the total number of people with HIV/Aids in Thailand was projected at 1,092,327. Of them, about 550,000 died, while another 540,000 or so infected people required continuing care and treatment. Among those infected were some 50,000 children born of HIV-positive mothers.

Thailand's past achievements in the fight against Aids have been well documented, and our effective strategy against the first wave of the Aids epidemic in the 1980s became a case study for many other developing countries that were struggling to cope with the problem at the time. Thailand has also been held up as a role model for its success in fighting the stigmatisation of people with Aids. But the country soon found it could ill afford to rest on its laurels.

No single strategy that worked in the past can be expected to deliver a similar success, given the evolving patterns of how HIV/Aids spreads among different population groups.

The overall prevalence of HIV/Aids may have declined, but the Kingdom is now discovering that the epidemic has expanded to cover a wider cross-section of the population. In the past, sex workers, homosexuals and intravenous drug users were most prone to HIV/Aids infection. The national strategy back then was to promote awareness and encourage condom use.

Nowadays, most cases of HIV/Aids transmission appear to involve heterosexuals outside the more traditional high-risk groups of commercial sex workers and intravenous drug users; for example, it is now not at all unusual for HIV to be passed between young adults and even spouses.

The successful awareness campaigns of the past targeting only high-risk groups cannot work today like they used to. The lesson the Kingdom needs to learn is there is no one single anti-Aids strategy. Thailand must adopt and adapt if it is to remain a step ahead of the changing patterns of the Aids epidemic, which will unfortunately be a major scourge of mankind for a long time to come.