Transmission via Injection Drug Use (IDU)

HIV transmission from IDU accounts for 15-25% of HIV infection globally and approximately one-third of HIV in­fection outside sub-Saharan Africa. The rate of HIV trans­mission for IDU is 0.0067 per exposure (see Figure 5) (Kaplan and Heimer, 1992). The majority of HIV-infected intravenous drug users live in Southern China, East Asia, the Russian Federation, and the Middle East. In some regions, such as Eastern Europe and Central Asia, approxi­mately 80% of incident HIV cases result from IDU (UNAIDS/WHO, 2006).

As there are approximately 13 million intravenous drug users globally, and 8.8 million in Eastern Europe and Asia, HIV prevention efforts targeting IDU are essential in curbing the rapid spread of HIV in these regions.

The greatest risk factor for HIV transmission via IDU is the use of contaminated syringes, needles, and other para­phernalia. This is most often associated with the practice of sharing drug paraphernalia, which can occur for cul­tural, social, legal, or economic reasons. Sharing with multiple injection partners is an added risk factor.

This can take place at sites where drugs are sold and injection equipment is made available for rental, such as in ‘shooting galleries’ (Marmor etal., 1987). Practices that increase risk when sharing include backloading, frontloading, and boot­ing. The first two occur when a drug solution is squirted from a donor syringe into another by removing the plunger (backloading) or needle (frontloading) from the receiving syringe. Booting is the practice of repeatedly drawing blood into the syringe and mixing it with drug.

In addition to drug practices, the type of drug may be important. The use of cocaine has shown higher risk of HIV transmission when compared to heroin (Anthony et al., 1991), perhaps due to the need for more injection frequency and also the more frequent practice of booting in cocaine drug injection. Also, cocaine is associated with high-risk sexual practices.

Another risk factor that is intimately linked with IDU is commercial sex work (Astemborski et al., 1994). Drug users often have to fund their habits by working as sex workers and drug-using commercial workers are less likely to use condoms than nonintravenous drug users. HIV epidemics in China, Indonesia, Kazakhstan, Ukraine, Uzbekistan, and Vietnam are fueled by the overlap of commercial sex work and IDU (UNAIDS/WHO, 2006).

One way to decrease the risk of HIV transmission among intravenous drug users is through cessation of drug injection. Methadone or buprenorphine replace­ment has been associated with a decrease in risk of HIV infection among users as a result of decreases in drug use (Sullivan et al., 2005). However, pharmacotherapy has overall been unsuccessful in complete cessation of IDU (Amato et al., 2004). Other methods to decrease the risk of HIV include syringe and needle exchange programs.

These programs offer clean syringes and needles in exchange for used injection equipment, with the goal of decreasing needle and syringe sharing. Several studies in the United States, the United Kingdom, and the Nether­lands have shown them to be effective (Buning et al., 1988; Donoghoe etal., 1989; Watters etal., 1994). Despite studies that show decreased needle sharing, there has been much controversy surrounding these programs due to concerns that the programs are condoning drug use and may increase the prevalence of drug use by making syringes and needles more available. These concerns have not been validated in other studies in the United States, Britain, France, Sweden, and the Netherlands, which showed no increase in the prevalence of drug use in the setting of needle exchange (Brickner et al, 1989; Oliver et al., 1994; Paone and Des Jarlais, 1994). An additional benefit of needle exchange programs is that they provide an oppor­tunity for counselors to educate drug users about preven­tive interventions.