Needle exchange is AIDS prevention that works. While no one wants to have to put on a condom, every drug user prefers injecting with a clean needle. In 2003, an academic review of 99 cities around the world found that cities with needle exchange saw their H.I.V. rates among injecting drug users drop 19 percent a year; cities without needle exchange had an 8 percent increase per year. Contrary to popular fears, needle exchange has not led to more drug use or higher crime rates. Studies have also found that drug addicts participating in needle ­exchanges are more likely to enter rehabilitation programs. Using needle exchange as part of a comprehensive attack on H.I.V. is endorsed by virtually every relevant United Nations and United States-government agency.

All over the world, however, solid evidence in support of needle exchange is trumped by its risky politics. Harm reduction is thought by politicians to muddy the message that drug use is bad; to have authorities handing out needles puts an official stamp of approval on dangerous behavior. Consider the United States. In 1988, Congress passed a ban on the use of federal money for needle exchange; President Clinton said he supported needle exchange but never lifted the ban, and it remains in effect. It not only applies to programs inside the United States but also prohibits the U.S. Agency for International Development from financing needle-exchange programs in its AIDS prevention work anywhere in the world. The administration of George W. Bush made the policy more aggressive, pressuring United Nations agencies to retract their support for needle exchange and excise statements about its efficacy from their literature. (Today, U.N. agencies again recommend that needle exchange be part of H.I.V.-prevention services for drug users.) Despite Barack Obama’s campaign pledge to overturn the ban, his first budget retained it. The House of Representatives recently passed a bill that would lift the ban — but it includes a provision that would make using federal money for needle exchange virtually impossible in cities, where it is needed most.

There are some parts of the world — Western Europe, Australia, New Zealand — that do widely use harm-reduction strategies, including needle exchange. And programs have begun even in Iran, of all places, which offers needle exchange and methadone; its program of giving prisoners methadone is now the world’s largest. China is now taking AIDS seriously, beginning to institute government-sponsored harm reduction nationwide. But the overwhelming majority of drug injectors around the world still have no such access. Because government financing is so politically unpopular, in most of the 77 countries that offer needle exchange, the programs are run by nongovernmental groups. As a result, these efforts are small, isolated and often undermined by uncooperative police and health departments. The world is casting aside the single most effective AIDS prevention strategy we know.

Russia needs needle exchange more than any other country: its H.I.V. epidemic is large, one of the fastest-growing in the world, and perhaps the most dominated by injecting drug use. Yet the needle-exchange efforts that do exist are scarce, small and under siege. I traveled there recently to see what lessons they hold. At 9 p.m. on a May night, in a tough neighborhood in Moscow’s north, I joined two young men as they climbed the stairs from the Metro. Arseniy and David were in their late 20s, wearing jeans and baseball caps. They had arrived to give out clean needles and promote harm reduction — but theirs was a guerrilla effort.

Image Credit... Raquel Aparicio

Needle exchange is legal in Russia — sort of. It must follow federal regulations. The catch is that these regulations don’t exist: the Federal Drug Control Service, whose top officials have called needle exchange “nothing more than open propaganda for drugs,” has been sitting on them for five years. As a result, no new harm-reduction programs have started during that time. Old ones continue where local authorities tolerate them, but Moscow’s government disapproves of needle exchange. So like their clients, Arseniy and David avoid the police. One of their clients was Masha, who, like every other drug user I interviewed, talked about police extortion. It is every addict’s main fear, but avoiding police shakedowns means only more dangerous injecting: if you fear being caught walking around with a needle, you use the community needle your dealer provides.