A study reveals that three million of the 15.9 million injection drug users (IDUs) throughout the world are likely to be HIV-positive.

The study, which was published recently in the Lancet, was conducted by reviewing injection drug use and the prevalence of HIV/ AIDS among IDUs in 148 countries. The research was led by Bradley Mathers of the National Drug and Alcohol Research Centre at the University of New South Wales.

According to the study, China has the largest number of IDUs with a mid-range estimate of 2.35 million IDUs and an HIV prevalence of 12.3 % among the group. The United States has the second highest case load with 1.85 million IDUs and an estimated prevalence among them of 15.6%.

Researchers also noted countries with potentially high HIV prevalence rate among IDUs such as Ukraine and Russia, which could be 42% and 37% respectively. Aside from Ukraine, the HIV prevalence rate above 40% among IDUs is seen in Argentina, Brazil, Estonia, Indonesia, Kenya, Myanmar, Nepal, and Thailand. Another interesting observation is that the lack of data from Africa, the Middle East, and Latin America could be masking a larger issue on a worldwide scale.

Data on injection drug use was available for only 13 out of 47 countries in sub-Saharan Africa, which Mathers attributed to "a constellation of risk factors" including high levels of socioeconomic hardship and the fact that many countries in the region are sources of illegal drugs being smuggled to Europe.

At the opposite side of the list, Australia and New Zealand have low HIV prevalence rates among injection drug users despite its high number of users, which researchers attributed to the quick introduction of needle-exchange program during the 1980s. Australian has about 1.5% of HIV-positive IDUs, while there is 1.6% prevalence rate among IUDs in New Zealand.