Injection Drug Use and Hiv Infecti... Health Article

INJECTION DRUG USE AND HIV INFECTION

Injection drug use (IDU) contributes to considerable illness burden in both developed and developing countries. Transmission of blood-borne pathogens (e.g., HIV, hepatitis B and C virus, Human T-Cell Lymphotrophic viruses I and II, and malaria) occurs primarily through direct sharing of needles or multi-person use of syringes. More recent studies suggest potential additional risks posed by shared use of injection paraphernalia (e.g., cookers, cotton, water), which is especially a concern with respect to transmission of hepatitis B and C viruses.

Human immunodeficency virus/acquired immunodeficiency syndrome (HIV/AIDS) and injection drug use can be considered as two intertwining epidemics. Socioeconomic, legal, and cultural factors and migration contribute to the emergence of drug injection. Injection drug use has been reported in 144 countries worldwide, among which 128 have detected HIV among injection drug users (IDUs). Although IDUs presently account for 5 to 10 percent of cumulative adult HIV infections worldwide, injection drug use is the predominant mode of HIV transmission in most of Western and Eastern Europe, North Africa, the Middle East, and increasingly in parts of Asia. Taking into account direct transmission among IDUs through sharing of contaminated injection equipment, and indirect transmission to sexual partners and offspring, injection drug use accounts for 44 percent of reported AIDS cases in Europe and nearly one-third of cases in the United States and the Southern Cone of South America. In the United States, approximately half of all new HIV infections are among IDUs. In Canada, the proportion of AIDS cases attributable to injection drug use is steadily increasing.

IDU-associated HIV epidemics are characterized by a high degree of regional and local heterogeneity. Explosive epidemics have occurred in both developing and developed countries or regions, with documented HIV incidence rates reaching as high as 20 to 30 percent per year. Early examples of HIV epidemics among IDUs were documented in Manipur, India Milan, Italy, Bangkok, Thailand, and New York City, suggesting that once HIV prevalence reaches a threshold of approximately 10 percent, it can surpass 40 to 50 percent within one to four years. More recently, Vancouver, Canada, witnessed an HIV outbreak with incidence reaching 18.6 per 100 person-years, despite an extended period of low stable HIV prevalence and a high-volume needle exchange program. In the Ukraine, over 100,000 HIV infections occurred in a single year, mostly due to sharing of injection equipment. These examples serve to illustrate the extent to which IDU-associated HIV epidemics can occur with startling speed. In such cases, subsequent spread to heterosexual non-IDU populations is almost imminent, which underscores the need for swift prevention measures.

In contrast, Australia and the United Kingdom have essentially averted widespread transmission of HIV among drug users. These prevention successes did not occur by chance. The early introduction of interventions such as widespread legal access to sterile injection equipment and expansion of methadone maintenance treatment programs likely spared these regions from the tragedies described above. Preventive strategies to curtail HIV transmission among IDUs are discussed in more detail below.