In much of Asia, the AIDS pandemic is driven primarily by injection drug use. In the former Soviet bloc, the rampant spread of AIDS is almost entirely the result of shared needles. Even here in Canada, shooting up is a critical vector for the spread of AIDS: In 2002, injection drug use caused one-quarter of new HIV cases; in 1996, it was the source of one-third of new infections. So when the 15th International AIDS Conference was held in Bangkok recently, one would have reasonably expected that injection drug use and our policies for dealing with it would have featured prominently in the flood of government statements, media reports and commentary that poured out. They didn't. There was much talk about sex, particularly the ideologically driven condoms-versus-abstinence debate. The high cost of drug treatments, and how to make them available in poor countries, was also well discussed. But that was about it. Writing in the National Post, Aileen Carroll, Canada's minister for international co-operation, went on at length about Canada's "strong leadership" in the fight against AIDS -- the money we spend, the committees we sit on, the programs we started. She went into some detail about condoms and how we are "addressing gender equality." She even found space to note that "Irish rock star and AIDS activist Bono" thinks the government's plans are "smart policy." And yet Ms. Carroll did not write so much as a single word about one of the key sources of the AIDS pandemic, in Canada and around the world. The cause of the maddening unwillingness to talk honestly about injection drug use is an open question, but there are surely at least two factors involved. The first is simply who the victims are, or rather how we see them. They're druggies. Junkies. Pariahs. Criminals. Few of us would explicitly write them off, but there's a feeling that, hey, they broke the law and brought it on themselves. They're not the innocent victims we prefer to be objects of our compassion. We've seen this sort of stigma before. In the early 1980s, when homophobia was more widespread and AIDS was annihilating gay communities, sympathetic portrayals of AIDS victims almost always focussed on kids who got the virus from their mothers or adults infected by tainted transfusions. Gay men got AIDs doing you-know-what and it was just a lot easier to talk about doe-eyed children -- just as it's easier today to ignore infected junkies and talk about African housewives infected by philandering husbands. A second factor stifling full discussion, one unique to official circles, is even less excusable. It's fear -- fear of where a serious, open look at AIDS among injection drug users would lead. Any discussion of AIDS and drug users would inevitably raise some basic questions, like what role does the law play? The law forbids the sale of drugs, so users can only get them from the black market. And it forbids the possession of drugs, which makes users criminals. What does this do to the behaviour of users? Why is it that users share needles knowing they could get HIV? Or an even simpler question: Why do they shoot up at all? There are many ways of taking drugs that don't risk infection and death. So why do they stick needles in their veins? These questions may look modest, but they're explosive. Dig around for answers and you will come across unsettling facts. By an odd coincidence, the host country of the AIDS conference, Thailand, is an ideal illustration. Ms. Carroll wrote her op-ed in Bangkok and she talked about meeting with Thai prostitutes and a dying woman in a hospice. But she neglected to mention the role of drugs in Thailand's AIDS epidemic. Here's what Ms. Carroll didn't say. For centuries, many Thais smoked opium. But at the beginning of the 1960s, users suddenly switched to heroin, a derivative of opium that is far more potent. And instead of smoking the drug, users injected it into their veins. When AIDS arrived in Thailand in the 1980s, it raced through the population on two superhighways: prostitutes and heroin-injecting drug users. Authorities responded to the first vector with condoms, education and other programs that successfully controlled the outbreak. But with drug users, the government stuck to its strict law-and-order approach. It didn't work. AIDS continued to spread among injectors, and from them to the general population. Today, one-third of new HIV cases in Thailand are caused by shooting up. Obviously, the story would have been very different if Thais had not abandoned opium smoking for heroin injection. So why did they do it? They had no choice. The law made them do it. At the urging of the U.S., the Thai government banned opium smoking in 1959. With the drug pushed into the black market, prices soared and users became desperate to get the "best bang for the buck." That meant using a more powerful form of the drug -- heroin instead of opium. It also meant switching to the drug-taking method that minimizes waste -- intravenous injection. In just a few years, prohibition replaced opium smoking with heroin injection and Thailand became an epidemic waiting to happen. The same tragedy unfolded elsewhere, including Canada: The prohibition of drugs pushed users to take up injection, and injection spread AIDS far and wide. These facts are clear, but don't expect official sources to acknowledge them. Among governments, drug prohibition is holy writ, an unquestioned and unquestionable good. To examine the evidence is impolitic. To express doubt is heresy. It's not that doubts don't exist. Far from it. Many public-health researchers have told me they think prohibition is a terrible mistake, that to deal with AIDS, hepatitis and other health threats we need to rethink our drug policies from the ground up. But they rarely say so publicly. They know that such heresy would jeopardize government contracts and jobs. One who has dared to speak the unspeakable is Dr. Martin Schechter, a leading AIDS researcher and chair of epidemiology at the University of British Columbia. "List the harms associated with, say, heroin," Dr. Schechter said in an interview last year. "List them in two columns, one associated with the pharmacological action of the drugs and the other column being the byproducts of prohibition and the war on drugs. Under the pharmacological column, for heroin, you would list two things. It causes euphoria and it is extremely addictive. Those are the two harmful things that you have to put on the wrapper of the medicine bottle if you were selling it. "But look at all the things in the other column. The HIV and hepatitis C epidemics. They don't come from the drug. They come from the fact that people are sharing contaminated needles in back alleys. If you look at overdoses, it's because the drugs are cut (adulterated), they're of unknown potency, they're taken in varying and unknown doses, so there's no control over what people are taking. All of the bacterial infections of the heart and abscesses are all due to the unsterile conditions as a result of prohibition. All of the violence, the corruption, the crime, the criminal-justice costs, the policing, the prisons, all of that is due not to the pharmacology of the drug, but the war on drugs." For the custodians of the status quo, this is scary stuff. It doesn't call for a committee to be struck. It can't be satisfied with a new program or an international conference. It demands nothing less than a revolution in public policy. Few, if any, of our politicians have the courage to even imagine such an exercise. And that is why, when talk turns to AIDS, it's just a lot safer and easier to avoid the subject of injection drug use altogether and stick to condoms and committees and what Bono thinks.