Opioid use disorder and HIV

Transmission among People Who Inject Drugs (PWID) early in the HIV epidemic

Soon after the identification of acquired immune deficiency syndrome (AIDS), it became clear that injection drug use was a major risk factor for the acquisition of human immunodeficiency virus (HIV). Des Jarlais and colleagues tested for HIV antibodies in stored sera from people who inject drugs (PWID) who entered opioid treatment programs in New York City and found that HIV seroprevalence increased from below 10% in 1978 to 50% in 1983, with stabilization thereafter [ ]. This observation highlights the rapidity with which HIV was able to spread in an unprepared and underresourced population of PWID. However, the finding that HIV seroprevalence plateaued at 50%–60% contrasted with hepatitis B virus seroprevalence of greater than 80% in studies of PWID, suggesting that HIV was less infectious in this context than hepatitis B virus. Other studies identified HIV nucleic acids in 39%–68% of used syringes recovered by syringe service programs (SSPs) or retrieved from shooting galleries [ , ].

Analyses, using varying methods, estimate that the transmission risk for a single episode of needle sharing from an HIV-positive to an HIV-negative individual is approximately 7 per 1000 exposures, with a range from 6 to 16 per 1000 [ , ]. Compared with other transmission risks [ ], needle sharing is more risky (per episode) than penile-vaginal intercourse or accidental needlesticks, but slightly less risky than unprotected receptive anal intercourse, and much less risky than the transmission risk from mother to child or from a blood transfusion from an HIV-positive source patient ( Table 5.1 ).

Viral load in the source individual is a strong and consistent determinant of HIV transmission across all exposure categories [ ]. Among PWID, behaviors that increase the risk of HIV acquisition include frequency of sharing, younger age, injecting in shooting galleries [ ], concurrent sexual risk factors [ ], and use of syringes with relatively high dead space [ ].

The (largely unheralded) success of HIV risk reduction among PWID

According to estimates from the Centers for Disease Control and Prevention (CDC), PWID accounted for over 30,000 new HIV infections annually in the late 1980s, and, briefly, had a higher rate of new infections than men who have sex with men (MSM) [ ]. By the early 1990s, HIV incidence rates had fallen sharply for both MSM and PWID, but while MSM-related incidence rebounded and tracked upward through 2006, PWID-related infections continued on a downward course. In 2015, the most recent year for which the CDC has estimates [ ], only 2200 HIV infections were attributed to injection drug use, 5.7% of HIV infections that year (another 1200 infections were attributed to men with same sex exposure and injection drug use). In a long-running community-based cohort study of PWID in Baltimore, the HIV incidence declined from 4.6% annually in 1988 to near 0% by 2001 [ ], and a similar decline in estimated HIV incidence among PWID in New York City was reported in serial cross-sectional surveys [ ]. Compared with the late 1980s peak, HIV infections attributed to injection drug use have declined over 90% nationally, an accomplishment second only to the decline in infections attributed to mother-to-child transmission [ ]. Fig. 5.1 shows the numbers of adults and adolescents diagnosed with AIDS by calendar year since 1985. Although AIDS diagnoses are not necessarily an accurate reflection of new infections, this figure underscores the long-term success of reducing HIV disease attributable to injection drug use.

Reduced needle sharing and syringe service programs

Between 1991 and 1994, the estimated number of clean syringes provided in New York City increased fivefold to 1.3 million per year [ ]. Among PWID recruited in New York City, receptive needle sharing in the prior 6 months declined from 42% in 1990–91 to 24% in 1996–97. In tandem with reduced injection-related risk, reported use of SSPs and HIV testing approximately doubled over this same time period [ ]. Additionally, PWID who were aware of their HIV-positive status when surveyed reported 65% lower odds of unsafe sex with and 37% lower odds of distributive syringe sharing (behaviors that put others at risk), but no difference in receptive needle sharing, compared with other PWID, highlighting the importance of HIV diagnosis in supporting behavioral changes that reduce the risk of onward transmission [ ]. In addition to providing access to clean needles/syringes, SSPs provide additional services to this hidden and difficult to reach population, including HIV testing, wound care, and referrals to drug treatment programs.

Although never evaluated in a randomized controlled trial, a wealth of observational data supports the benefits of SSPs in reducing HIV transmission and dispels concerns that providing clean syringes encourages drug use [ ]. The CDC [ ], the Institute of Medicine [ ], and the World Health Organization and other international health organizations [ ] strongly endorse SSPs as an essential service for PWID to reduce HIV transmission.

The full potential benefits of SSPs in the United States have not been realized due to inadequate support and implementation. Political support for SSPs has been tepid and grudging at best, and outright hostile at worst. The Netherlands, the United Kingdom, and Australia began implementing robust SSPs in the 1980s when the rapidity of HIV transmission among PWID became clear. At that time in the United States, almost all states had laws criminalizing possession and distribution of drug paraphernalia, which could be invoked against SSPs. In 1988, the federal government instituted a ban on federal funding for SPPs, which has remained in effect since, with the exception of a one-year period in 2009 [ ]. Consequently, legislative support and funding for SSPs has been left up to state and local governments, with substantial heterogeneity across states. In a 2014 review of state laws in 36 states with available data, there were 10 states that had not passed laws explicitly authorizing SSPs and provided no public funding for SSPs [ ]. In this analysis, the authors found a correlation between an absence of state-level funding for SSPs and unfavorable trends in HIV incidence among PWID in the state. A global systematic review of PWID services conducted in 2010 [ ] estimated that only 22 needle/syringes were distributed per PWID per year in the United States, a distribution rate that lagged not only Canada (46 per PWID per year) and Western Europe (59 per PWID per year) but also central Asia (92 per PWID per year), south Asia (37 per PWID per year), and east and southeast Asia (30 per PWID per year). For reference, the WHO has recommended a target distribution rate of at least 200 clean syringes per PWID per year. Revealingly, a 4-year follow-up to this report assessed the six countries with the largest numbers of PWID (China, Malaysia, Russia, Ukraine, Vietnam, and the United States) and found that only two countries had made no progress in expanding coverage of SSP, medication-assisted treatment (MAT), or antiretroviral therapy (ART) to PWID since the original report—Russia and the United States [ ]. By virtue of preventing HIV infection and being relatively inexpensive per person served, expansion of SSP in the United States is highly cost-effective [ ].