16 million people worldwide inject drugs, with 3 million infected with HIV, according to a study published in the September 24th edition of The Lancet. High levels of HIV infection amongst injecting drug users were observed in south and south east Asia, eastern Europe and Latin America. However, the investigators’ study was limited by a lack of reliable data from many countries, most notably in sub-Saharan Africa, an indication of the neglect of the HIV prevention needs of injecting drug users.
Injecting drug use has caused health problems around the world, not least the transmission of bloodborne infections, most notably HIV. Accurate and reliable estimates of the number of injecting drug users and HIV prevalence amongst them is needed so that appropriate and targeted health promotion interventions can be designed.
Such estimates are now four years out of date. There are a number of difficulties developing such estimates. Because injecting drug use is an illegal and stigmatised behaviour, estimates from population based surveys are often under-estimates. Furthermore, many developing countries do not have surveillance systems in place.
A team of investigators based in Sydney, Australia, therefore conducted a literature search in August 2007 to try and establish the number of injecting drug users aged between 15 - 64 around the world and HIV prevalence amongst them. Their search included both peer-reviewed papers and what that called “grey literature” – estimates that had not been subjected to the rigorous analysis of peer review.
The investigators’ search revealed that injecting drug use was reported in 148 countries. Surveillance information was extremely patchy for some world regions with only six of the 15 countries in the Caribbean reporting injecting drug use and 13 of the 47 countries in sub-Saharan Africa.
There were also weaknesses with the surveillance information available from richer countries. The information on the extent of injecting drug use from Belgium, Denmark, France, Ireland, Italy, Spain and Switzerland all dated to before 2000.
Nevertheless, the investigators calculated that the 0.363% of the population in the countries supplying data were injecting drug users. Estimates of the proportion of injecting drug users in individual countries ranged from only 0.02% in India and Cambodia to over 5% in Azerbaijan. There were also considerable variations in regional estimates, with 0.056% of the population estimated to inject drugs in south Asia but 1.5% of the population in eastern Europe. In the UK, an estimated 0.39% of the population inject drugs.
Based on this data, the investigators estimated that there are 15.9 million individuals around the world who inject drugs.
Next the investigators calculated HIV prevalence amongst injecting drug users. This estimate was based upon data from 128 countries. The investigators note that 85% of their estimates regarding HIV prevalence are based upon information contained in “grey literature.”
Prevalence varied considerably between individual countries, ranging from 0.01% in eight countries to over 72% in Estonia. In nine countries HIV prevalence amongst injecting drug users was over 40%, including Argentina (49.7%), Brazil (48%), Kenya (42.9%), Nepal (41.39%) and Thailand (42.5%). In a further five countries prevalence was between 20% - 40% including Cambodia (22.8%), Russia (37.15%) and Spain (39.7%). In the UK, an estimated 2.3% of injecting drug users are HIV-positive.
HIV prevalence varied significantly within some countries. In Russia, 0.3% of injecting drug users are HIV-infected in Pskov, compared to 12% in Moscow, 32% in St Petersburg and 74% in Biysk.
Overall, the investigators calculated that 3 million injecting drug users around the world are HIV-positive, the largest populations of HIV-infected drug users being in eastern Europe, south and southeast Asia and Latin America.
Concern is expressed by the investigators about the lack of information about the scale of injecting drug use in some world regions, particularly sub-Saharan Africa, the world region with the highest HIV prevalence, where they believe “a constellation of risk factors” exist for the development of injecting drug use.
They also note the dynamism of the HIV epidemic amongst injecting drug users. In the late 1990s there were few HIV infections amongst injecting drug users in Estonia, but one study suggests that 72% are now infected.
“There is a clear mandate to invest in HIV prevention activities such as needle exchange and syringe programmes and opioid substitution treatment and to provide treatment and care for those living with HIV/AIDS”, conclude the investigators. They add, “the magnitude of the risk has not been met with an equally concerted investment in research to quantify the problem.”
An accompanying editorial comments on the “disturbing trends” of HIV prevalence amongst injecting drug users and says that “it should be an imperative – for both resource-constrained countries and international donors –to implement large-scale evidence-based programmes of HIV prevention whenever there is an indication of a problem with the development of injecting drug use.”
Mathers B.M. et al. Global epidemiology of injecting drug use and HIV among people who inject drugs: a systematic review. The Lancet (online edition), September 24th, 2008.
Arasteh K. et al. Injecting drug use, HIV, and what to do about it. The Lancet (online edition), September 24th, 2008.