An estimated three million injecting drug users around the world are infected with the Aids virus, a study suggests. Data from 61 countries indicates that almost 16 million people may be injecting themselves with heroin and other drugs. In nine countries, the proportion of HIV-positive injecting drug users (IDUs) among people aged 15 to 64 was more than 40%. Two countries with exceptionally high rates of HIV-positive injecting drug users were Argentina (49.7%) and Estona (72.1%). In the UK, 0.39% of 15 to 64-year-olds injected drugs, of whom 2.3% were reported to be HIV positive. Dr Bradley Mathers, from the University of New South Wales in Sydney, Australia, and colleagues report the findings in an early online edition of The Lancet medical journal. They wrote: "We estimate that, worldwide, about three million people who inject drugs might be HIV positive."