METHODS: Collation and review of existing estimates of IDU prevalence and HIV prevalence from published and unpublished documents for the period 1998-2003. The strength of evidence for the information was assessed based on the source and type of study.

RESULTS: Estimates of IDU prevalence were available for 130 countries. The number of IDU worldwide was estimated as approximately 13.2 million. Over ten million (78%) live in developing and transitional countries (Eastern Europe and Central Asia, 3.1 million; South and South-east Asia, 3.3 million; East-Asia and Pacific, 2.3 million). Estimates of HIV prevalence were available for 78 countries. HIV prevalence among IDU of over 20% was reported for at least one site in 25 countries and territories: Belarus, Estonia, Kazakhstan, Russia, Ukraine, Italy, Netherlands, Portugal, Serbia and Montenegro, Spain, Libya, India, Indonesia, Malaysia, Myanmar, Nepal, Thailand, Viet Nam, China, Argentina, Brazil, Uruguay, Puerto Rico, USA and Canada.

METHODS: We conducted a systematic review searching MEDLINE, Scopus, Web of Science, Cochrane Central Register of Controlled Trials and PsycINFO for studies published from January 2000 to March 2019. Reference lists and conference proceedings were hand-searched. Observational and intervention studies were eligible for inclusion. Risk of bias was assessed using the Risk of Bias in Non-Randomised Studies of Interventions (ROBINS-I) tool. Meta-analyses were conducted using random-effects models.

RESULTS: Of 13 373 records identified, 11 studies from Australia, Europe, Malaysia and the United States were included. All studies had at least a serious risk of bias, largely due to confounding and selection bias, making it difficult to draw causal conclusions from the evidence. Ten studies provided data on the association between current OAT use and recent HIV testing. Six showed a positive association, while four provided little evidence of an association: pooled odds ratio (OR) = 1.71, 95% confidence interval (CI) = 1.28-2.27. Looking at having ever been on OAT and having ever been HIV tested, seven studies showed a positive association and three showed either weak or no evidence of an association: pooled OR = 3.82, 95% CI = 2.96-4.95.

METHODS: We conducted a systematic search of peer-reviewed (Medline, Embase, PsycINFO), internet, and grey literature databases, from January 2000 through 2nd June 2025 and engaged international experts and relevant agencies liaising with key agencies focused on incarcerated populations (WHO, UNODC, UNAIDS and EUDA). Data on study methods, size of incarcerated populations and demographic characteristics, and prevalence of IDU, HIV, HCV, HBV and tuberculosis among incarcerated populations were extracted. Meta-analyses pooled data where multiple estimates were available for a country; regional and global estimates were calculated, weighted by incarcerated population size. We present overall country, regional and global prevalence estimates for each variable examined, stratified by sex. We then estimated the ratio of IDU, HIV, HCV, HBV and tuberculosis prevalence among incarcerated populations compared to the general population.

RESULTS: Of 75,755 screened documents, 2,968 were eligible for data extraction. There are approximately 11,322,000 people aged 15-64 years incarcerated globally with their incarceration rate being 221 per 100,000 (29 per 100,000 among females and 404 per 100,000 among males). Substantial variation in rates across countries and regions were observed with the highest regional rate being in North America. Globally, we estimate that 11·9% of people who are incarcerated have ever injected drugs (1,348,000; 95%CI 1,061,500-1,687,000), 51·4 times higher than the general population. We estimate that 3·7% (95%CI 2·5-5·4) of people who are incarcerated globally are living with HIV (25.1· times higher than the general population); 11·7% (95%CI 7·7-17·1) have current HCV infection (15·6 times higher); 4·4% (95%CI 2·4-7·7) have current HBV infection (2·2 times higher) and 2·5% (95%CI 1·5-3·8) have active tuberculosis (45·3 times higher than the general population). There is substantial variation geographically and among females and males.

CONCLUSION: The substantial concentration of people with multiple risks and comorbidities requires improved strategies to screen, evaluate, treat and prevent these adverse consequences, which is crucial for global control efforts.

METHODS: We conducted a systematic review of evidence for provision of opioid agonist treatment (OAT), needle syringe programs (NSPs), HIV testing and antiretroviral therapy (ART), hepatitis C virus (HCV) testing and direct-acting antiviral (DAA) treatment, tuberculosis screening and treatment, hepatitis B virus (HBV) testing, treatment, and vaccination in carceral settings. We searched from peer-reviewed and grey literature databases between 2000 and 2025 and used the most recent data available for each indicator.

FINDINGS: OAT was documented in 59/207 countries (29 %), and NSPs in ten (5 %). HIV testing was documented in 86 countries (42 %) and ART in 79 countries (38 %). HCV testing was confirmed in 55 (27 %), with DAA treatment in 47 (23 %). HBV testing was identified in 51 countries (25 %), treatment in 36 (17 %), and vaccination in 41 (20 %). Tuberculosis screening was documented in 96 countries (46 %) and treatment in 81 (39 %). Fewer than 2 % (approximately 172,000) of the 11.3 million people incarcerated worldwide live in countries that offer OAT, NSPs, and treatment for HIV, HCV, HBV, and tuberculosis in at least one carceral facility. There is not a single country where incarcerated people have access to all such services in every facility. Programme level evidence was rarely available.

INTERPRETATION: The global shortage of services that prevent and treat infectious disease and harms related to injecting drug use in carceral settings is a critical public health issue and, compared with community standards, a breach of human rights. This study underscores the urgent need for international collaboration and policy reform to scale up and stabilise services that address the health needs of incarcerated populations, ultimately improving health outcomes for both incarcerated populations and wider community.