Study results suggest strong associations between the injection network size of people who use injection drugs and both needle sharing behavior and HIV viral suppression.


Injection drug use, for most individuals, is inherently a social activity, according to Javier A. Cepeda, PhD, MPH. Therefore, once a blood-borne disease, such as HIV, enters an injection drug network, transmission can diffuse rapidly, he says. Even those who inject with just one partner put themselves and others at risk, as their partner’s partners must be considered. Conversely, evidence suggests that transmission of HIV is much less likely to occur when HIV-positive individuals are virally suppressed. However, research specifically examining injection drug networks and viral suppression is lacking.


Characterizing PWID With HIV

For a study published in the Journal of Acquired Immune Deficiency Syndrome, Dr. Cepeda and colleagues examined the associations between injection network size, syringe sharing, and viral suppression. “We characterized individuals who reported being in large injection drug networks (injecting with more than 10 individuals in the past 30 days) in terms of their risk behaviors and viral suppression,” he explains. “Thus, we wanted to answer a few basic questions: (1) Do individuals with large injection networks frequently share syringes? (2) Are those with large injection networks who are infected with HIV being treated (ie, virally suppressed)? The latter is important because of benefits to the individual and their injection or sexual partners who are HIV negative.”

The study team recruited nearly 15,000 people who inject drugs (PWID) across 15 sites for their cross-sectional study. Interviewer-administered questionnaires were used to assess network characteristics, substance use, HIV testing experience, and access to health services. Multilevel logistic regression was used to evaluate the relationship between injection drug network size and both syringe sharing at last injection and viral suppression (<150 copies/mL) among HIV-positive participants.


Key Findings

Participants in the study had an average injection network size of three, while 7% of participants injected with more than 10 members within the previous 30 days. “There was a strong, significant effect of larger networks and higher odds of syringe sharing,” says Dr. Cepeda. “In our unadjusted models, individuals who were in large networks had almost two-fold higher odds of syringe sharing at last injection when compared with those with no injection drug-using partners. However, this association was abated somewhat in the multivariable model.”

Dr. Cepeda and colleagues also examined qualitative measures of large injection networks, such as visiting shooting galleries, semi-anonymous locales where PWID can buy, rent, or borrow syringes. “We found a strong and significant association between shooting gallery attendance and syringe sharing,” Dr. Cepeda adds. “Thus, our quantitative and qualitative measures of injection drug networks supported each other.”

Similar associations were seen between larger injection drug network and viral suppression (Table). “In our multivariable model, individuals with the largest networks had the lowest odds of viral suppression,” says Dr. Cepeda. “Individuals who attended shooting galleries also had lower odds of viral suppression.”


Important Implications

While Dr. Cepeda and colleagues’ study was conducted in India, he believes their findings are applicable to clinicians in the United States. “The US

is currently experiencing a resurgent heroin epidemic, which may lead to a rise in injection drug use followed by transmission of HIV and hepatitis C,” he says .  “Many of the issues that we observed in India could have occurred in the US in the absence of harm reduction services (eg, syringe exchange programs, opioid substitution therapy), access to testing and treatment, and advocacy for people living with HIV. Doctors should ensure that patients who may be injecting drugs are doing so safely and if they do become infected, that treatment is initiated immediately. Susceptible individuals may receive additional prevention benefits if the individuals with whom they share syringes are virally suppressed.”


Cepeda J, Soloman S, Srikrishnan A, et al. Injection drug network characteristics are important markers of HIV risk behavior and lack of viral suppression. J Acquir Immune Defic Syndr. 2017;75:257-264. Available at

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Young A, Jonas A, Mullins U, et al. Network structure and the risk for HIV transmission among rural drug users. AIDS Behav. 2013;17:2341-2351.

Suh T, Mandell W, Latkin C, et al. Social network characteristics and injecting HIV-risk behaviors among street injection drug users. Drug Alcohol Depend. 1997;47:137-143.