Research focus

Understanding how many people inject drugs is critically important for the effective provision of public health and harm reduction services. However, the severe stigma that is often attached to injecting drug use, and illicit nature of this behaviour, means that it is often difficult to have a clear picture of how many people inject drugs in a given nation or region.¹ Without this basic population number, it is also difficult to know how many people who inject drugs are living with HIV or hepatitis C virus (HCV), or to know how well HIV and HCV prevention interventions such as needle and syringe programs and opioid substitution therapy are reaching people in need.

We sought to review evidence globally to estimate:

1. The number of people who inject drugs
2. Women and young people as a proportion of people who inject drugs
3. HIV and HCV antibody (anti-HCV) prevalence among people who inject drugs
4. Coverage of needle and syringe programs (NSP) and opioid substitution therapy (OST)

For each of these, we calculated national, regional and global estimates. Estimates were calculated from data presented in peer-reviewed literature and reports from government departments, non-government agencies, and international organisations such as UNAIDS and the Global Fund.

How many people inject drugs?

We used data from 976 separate sources to estimate that there are 15.6 million (uncertainty interval (UI) 10.2-23.7 million) people globally who inject drugs. This number refers to people who have injected drugs in the previous 12 months; there are no estimates of the number of people who have ever injected drugs. We found reports of injecting drug use occurring in 179 countries and territories, in all world regions. The highest prevalence of injecting drug use was in Eastern Europe, where an estimated 1.3% of the population injects drugs, compared to 0.33% globally.

Globally, women are one in five (20.4%) of all people who inject drugs, but that varies significantly between nations and regions. The lowest proportions of women are seen in South Asia (3.1%) and the Middle East and North Africa (3.5%). Some sources that we reviewed suggested that women who inject drugs in these regions are under-counted due to the extreme stigma and poor access to services that they encounter. The highest proportions of women in the injecting population were seen in North America (30.0%) and Australasia (33.4%).

Between one-quarter and one-third of people who inject drugs globally are young, defined as 25 years of age or under. Again, there was substantial variation between nations and regions. The highest proportions of young people in the injecting population were seen in Latin America (51.2%), Eastern Europe (41.8%), and the Middle East and North Africa (38.7%). In contrast, young people were just 6.7% of people who inject drugs in Central Asia.

What is the prevalence of HIV and HCV antibody among people who inject drugs?

Estimates of HIV and HCV antibody prevalence were calculated using data from 602 and 417 sources, respectively. Globally, 17.8% of people who inject drugs are living with HIV infection, and more than half (52.3%) of people who inject drugs have anti-HCV, indicating the potential for chronic HCV infection. Australia and New Zealand have among the lowest HIV prevalence among people who inject drugs globally, at 1.1%, but anti-HCV prevalence is above the global average, at 57.1%.

Table: Global and regional estimates of population size, HIV and anti-HCV prevalence, and coverage of harm reduction programs for people who inject drugs (PWID)

N.B. No data were identified for the Pacific Islands; see Degenhardt et al² for estimates for the Pacific Islands that are based on global data. For uncertainty intervals around the number of people who inject drugs, and HIV and anti-HCV prevalence, see Degenhardt et al.². For uncertainty intervals around estimates of NSP and OST coverage, see Larney et al.³

Are harm reduction services reaching people who inject drugs?

We used data from 234 source documents to estimate two indicators of coverage of harm reduction programs: the number of sterile needles distributed by NSP per person who injects drugs per year, and the number of OST recipients per 100 people who inject drugs. For each of these indicators, we categorised countries into three levels of coverage – low, moderate, and high – in keeping with World Health Organization definitions (see box below).

Globally, NSP coverage is low, at just 33 needle-syringes per person who injects drugs per year. By region, only Australasia had high coverage of NSP. Moderate coverage was estimated for Western Europe, with the remaining regions all having very low NSP coverage.

Similarly, coverage of OST was low, at 16 OST recipients per 100 people who inject drugs. In interpreting this finding, it is important to consider that not all people who inject drugs inject opioids, and not all opioid injectors will want or need OST. Thus, regions with high coverage of OST among people who inject drugs may still have poor coverage of OST among opioid dependent people if smoking is the dominant route of administration. If we are considering HIV and HCV prevention, however, coverage of OST among people who inject drugs is an important indicator. Western Europe and South Asia had the highest OST coverage (94 and 91 OST recipients per 100 people who inject drugs, respectively). Several regions with high HIV prevalence among people who inject drugs had very low coverage of OST, including Eastern Europe (1 OST recipient per 100 people who inject drugs) and Latin America (3 OST recipients per 100 people who inject drugs).

Harm reduction strategies are most effective at preventing HIV and HCV when provided in combination. Of 51 countries with an estimate of both NSP and OST coverage, only four had high coverage of both interventions: Australia, Austria, the Netherlands, and Norway. These countries include fewer than one per cent of all people who inject drugs globally. It is possible that there are other countries with high coverage of both NSP and OST, but the necessary data were not available.

Regional and national case studies

Sub-Saharan Africa: Opportunities to prevent further spread of HCV infection

We identified 36 countries in sub-Saharan Africa with evidence of injecting drug use, compared to a 2008 review that identified 13 countries in this region where people injected drugs.⁴ This increase is probably due to a combination of the spread of injecting to new countries, and better reporting of injecting drug use in countries where it has occurred for some time. We now have a much clearer picture of blood borne virus prevalence among people who inject drugs in sub-Saharan Africa. HIV prevalence is roughly equivalent to the global average, but anti-HCV prevalence is considerably lower than the average (21.8% as compared to 52.3%). This may be due to the relative recency of onset of injecting drug use in the region. This presents an opportunity to prevent a major HCV epidemic in this population (and to control and prevent HIV), but dramatic increases in NSP and OST coverage will be required. At present, only seven countries in the region provide NSP, and eight have OST. An estimated two sterile needles are distributed per person who injects drugs per year, and there is one OST recipient per 100 people who inject drugs. These estimates provide support for non-government organisations seeking to fund and implement NSP and OST on a greater scale. 

Russia: Lack of harm reduction responses and very high HIV prevalence

Russia has the third largest population of people who inject drugs globally (1.9 million), and among the highest HIV prevalence (30.4%) and anti-HCV prevalence (68.7%), but very poor access to harm reduction. There are few NSP services, and just 2 needle-syringes are distributed per person who injects drugs per year. OST is illegal and not available anywhere in the country. The number of new HIV infections in Russia is increasing (in contrast to global trends) and more than half of new HIV infections in the country are due to injecting drug use.⁵ In the face of strikingly high HIV and anti-HCV prevalence, increases in prevention, and HIV and HCV treatment, are urgently needed.

United States: Urgent need to scale-up services to respond to increasing injecting drug use

We estimated a population of 2.2 million people who inject drugs (the second largest globally) in the United States, but it is important to recognise that the situation is changing rapidly in light of the opioid epidemic and increasing heroin injecting. There have been multiple reports of HCV and HIV outbreaks, often among networks of young people injecting drugs or in rural areas with very limited access to harm reduction services.^6-8 There is an urgent need to bring service provision to scale, and for better data to understand where gaps in service provision exist. We have estimated that there are 30 needle-syringes distributed per person who injects drugs per year, but this may be an under- or over-estimate as not all programs report data on number of needle-syringes distributed. Additionally, we have estimated that there are 19 OST recipients per 100 people who inject drugs, but this number does not include people prescribed buprenorphine in office-based settings. Other research has suggested that there is a significant gap between OST system capacity and the number of people needing treatment, and that this is particularly acute in rural areas.⁹

Latin America and the Caribbean: Lack of data impedes development of responses

There were few data sources from the regions of Latin America and the Caribbean, despite known issues with injecting drug use in various countries in these regions. For example, the estimate of regional prevalence of injecting drug use for Latin America was based on data from 5 of 20 countries, and only one Caribbean territory (Puerto Rico) had an estimate of injecting drug use prevalence.  With such limited data, our estimates are necessarily uncertain. This lack of certainty impedes planning and the development of effective, targeted responses to injecting drug use and related harms.

Conclusion

These reviews have identified major gaps in epidemiological data and coverage of harm reduction interventions for people who inject drugs. Although there are a small number of countries with high levels of service provision, coverage is typically low and insufficient to prevent or halt HIV and HCV epidemics in this population. Significant investment in harm reduction services globally is required.

For further details, see the following open access papers:

Degenhardt et al. Global prevalence of injecting drug use and sociodemographic characteristics and prevalence of HIV, HBV and HCV in people who inject drugs: a multistage systematic review. Lancet Global Health, 2017;5:e1192-1207. http://www.thelancet.com/pdfs/journals/langlo/PIIS2214-109X(17)30375-3.pdf

Larney et al. Global, regional, and country-level coverage of interventions to prevent and manage HIV and hepatitis C among people who inject drugs: a systematic review. Lancet Global Health, 2017;5:e1208-1220. http://www.thelancet.com/pdfs/journals/langlo/PIIS2214-109X(17)30373-X.pdf

References

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