FRIDAY, Sept. 26 (HealthDay News) -- As the number of countries reporting intravenous drug use has increased over the last decade, a new study suggests that as many as 3 million of these addicts may be HIV-positive.

The data, published online in The Lancet, found the proportions of injecting drug users (IDUs) who are HIV-positive exceeds 40 percent in nine countries. Yet, the variation between countries is extreme.

For example, in the United States, just less than 1 percent of 15- to 64-year-olds are IDUs, 15.6 percent of whom are HIV positive; meanwhile in Argentina, the proportion of IDUs is far lower (0.29 percent), but the proportion of those with HIV is more than triple at 49.7 percent. In the United Kingdom, though, 0.39 percent of the same age group inject their drugs yet only 2.3 percent are thought to be HIV positive.

"Areas of particular concern are countries in southeast Asia, eastern Europe, and Latin America, where the prevalence of HIV infection among some subpopulations of people who inject drugs has been reported to be over 40 percent," the authors wrote.

While noting a dearth of information from Africa, they added that a "constellation of risk factors exists for the development of injecting drug use, as has occurred elsewhere."

The researchers estimate that almost 16 million people worldwide inject drugs. They identified 148 countries with IDU and 120 of those having HIV among IDUs, up notably from a 1998 review that found 29 countries with IDU and 103 with HIV among IDUs.

In an accompanying commentary in The Lancet, Kamyar Arasteh and Don Des Jarlais, of Beth Israel Medical Center's Baron Edmond de Rothschild Chemical Dependency Institute in New York, call for massive worldwide intervention.

"The one optimistic aspect of this rather gloomy situation is that, if HIV-prevention efforts are implemented on a large scale when prevalence is low in injecting drug users, it is possible to avert HIV epidemics in users. Thus it should be an imperative for both resource-constrained countries and international donors to implement large-scale evidence-based programs for HIV-prevention whenever there is an indication of a developing injecting-drug-use problem," they concluded.

More information

The U.S. Centers for Disease Control and Prevention has more about HIV/AIDS.