Injecting-related infections represent a significant, growing, and often overlooked component of the global health burden associated with people who inject drugs (PWID). According to a recent comprehensive review by Masters et al. in Clinical Microbiology Reviews, more than 4.7 million infections are estimated to occur each year among the 15 million individuals worldwide who inject drugs. These infections span a broad clinical spectrum—including skin and soft tissue infections (SSTIs), bacteraemia, infective endocarditis, osteomyelitis, septic arthritis, and invasive fungal diseases such as candidemia—and are frequently associated with high morbidity and largely preventable mortality.

The etiologic agents most frequently implicated include Staphylococcus aureus (including high rates of methicillin-resistant Staphylococcus aureus [MRSA]), Streptococcus pyogenes, Clostridium spp., and Candida albicans. The pathophysiology of these infections is complex: contamination may occur via non-sterile drug solutions, filters (e.g., cotton, cigarette filters), injecting equipment, or environmental sources (e.g., puddle water or saliva used as diluent). Black tar heroin, for example, is specifically associated with increased SSTI risk, necrotizing fasciitis, and even rare infections like mucormycosis and botulism.

Yet infection risk is not purely microbiological. Social determinants of health—homelessness, incarceration, psychiatric comorbidities, and healthcare stigma—are strongly associated with infection incidence and poor outcomes. Up to 75% of PWID experience psychiatric illness, and many report traumatic or discriminatory healthcare encounters, leading to delayed presentation or patient-directed discharge (PDD). In some cohorts, PDD rates reach 50%, contributing to high readmission and relapse rates.

Therapeutic approaches are evolving. While traditional management has relied on prolonged inpatient intravenous therapy, emerging data now support partial oral antibiotic regimens, shorter IV courses, and outpatient parenteral antimicrobial therapy (OPAT) in selected PWID. Observational studies suggest that, when integrated with addiction medicine services, outcomes with oral or OPAT strategies are comparable to inpatient IV therapy.

The authors advocate a multidisciplinary, person-centred framework to optimize infection management in PWID. This includes expanded access to harm reduction (e.g., needle and syringe programs, supervised injecting facilities), opioid agonist therapy, and linkage to community-based care. Ultimately, effective care requires confronting the systemic stigma that continues to undermine health equity for this population.

This review is essential reading for clinicians, public health professionals, and policymakers committed to reducing preventable infectious disease morbidity—and addressing one of the most urgent intersections of addiction, infection, and inequity.

Reference

Masters J, Goodman-Meza D, Russell D, et al. Bacterial and fungal infections in persons who inject drugs. Clin Microbiol Rev. 2025; e00162-23. https://doi.org/10.1128/cmr.00162-23