A couple of years ago Britain's leading HIV specialist Professor Brian Gazzard wrote an editorial in the Lancet, titled "Miracles do happen", about his astonishment at how Aids had become a treatable illness. A decade earlier it had seemed "highly unlikely an effective treatment would become available in the foreseeable future", but a vigorous research programme has identified several therapeutic "targets", and the combination of two, and then three, drugs in what became known as Highly Active Antiretroviral Therapy brought mortality rates crashing down. A recently diagnosed 25-year-old can now expect to survive three decades or longer, a life expectancy comparable to that for people with insulin-dependent diabetes. So credit where it is due, particularly to the much-maligned drugs industry that made it all possible.

Still the preferred option remains, as ever, prevention, for gratefully there are few diseases more readily preventable. Here the biological complexities of the Aids virus are irrelevant. The lowest of low-tech solutions - an abundant supply of condoms and sterile needles - is more than sufficient to stop 80 per cent of "transmission episodes" in their tracks. Then a judicious combination of screening blood transfusions for contamination and treating pregnant women infected with the virus should take care of the rest. And there are ample funds available - to the tune of $10bn a year, 40 times more than the total cost of the decade-long and logistically more complex smallpox eradication programme carried out in the 1970s.

How then to explain the "massive in-your-face failure of the HIV industry", as Elizabeth Pisani describes it, with 30 million people infected worldwide, two million deaths and a similar number of new infections (7,000 a day) last year alone? "It might have been even worse without our efforts," she writes, "though it is hard to see how it could be."

Ms Pisani should know better than most, having spent the best part of ten years within "the industry". As such her analysis inevitably extends beyond the practicalities of HIV prevention to touch on matters of more universal significance, confirming, regrettably, the common prejudice that the corruption and incompetence of international aid agencies are a major impediment to solving the problems that are ostensibly their raison d'être.

Her account begins in the mid-1990s when, recently recruited to UNAIDS, she finds her task is to "talk up" the threat posed by HIV into a potential pandemic, the better to galvanise the rich donor countries to increase their funding for its programmes. This has the desired effect, but her own reality check comes when, seconded to Jakarta, she encounters (and vividly relates) the bizarre subculture of the transsexual waria epitomised by Fuad, "a self-proclaimed heterosexual guy who has unpaid sex with a woman who sells sex to other men, while himself also selling sex to men and buying it from transgendered sex workers". Fuad may have pushed most "high-risk" buttons for HIV infection, yet "he didn't fit into a single one of our boxes". And therein lies the key to it all - recognising who in any particular society is having sex with whom, and how, and doing something about it.

That should not be too difficult. Indeed, the two countries that have pursued this approach, Thailand and Uganda, have been spectacularly successful in containing the spread of the virus. In the early 1990s, the Thai government, recognising the threat posed to its flourishing sex industry, imposed a mandatory 100 per cent condom-use edict on brothel owners, with the threat that any transgression would result in immediate closure. By contrast, in Uganda HIV was spread by (a lot) of unpaid sex where "plenty of women are having sex with people other than their husbands". Here, the universal distribution of condoms alone could never be effective without a major shift of sexual mores in favour of exclusively monogamous relationships.

But where Thailand and Uganda have led, international aid agencies have refused to follow. Fearful of being labelled judgemental or racist, Pisani claims, they would rather blame the epidemic on "poverty and underdevelopment" and devise ineffectual education programmes directed at the general population. Ten separate UN agencies have managed to inveigle their way on to the Aids bandwagon, its luminaries traversing the globe from one air-conditioned conference hall to the next promoting a stream of initiatives and reports where everyone "bar eunuchs and the already dead" are allegedly at risk.

It is probably mere illusion to suppose that The Wisdom of Whores will, as it certainly should, cause much heartsearching within the industry. But the mortality toll of Aids tells it all, and sooner or later reform must come. Regrettably, "for the foreseeable future", there will be two million people per year for whom it will come too late.