Canadian researchers have developed a new way to reduce the risk of HIV transmission among people who inject drugs (PWID) who share injection-drug preparation equipment, specifically, what are known as cookers.

Publishing their findings in two papers in the Journal of Acquired Immune Deficiency Syndromes, the investigators responded to a recent dramatic increase in the rate of HIV transmission among PWID in London, Ontario. This surge occurred despite Canada’s widespread use of syringe services programs and medication-assisted treatment for opioid use disorder.

Between August 2016 and June 2017, the investigators interviewed 119 PWID in the area about their injection-drug-use behaviors and HIV risk. Their analysis indicated that those PWID who shared drug-preparation equipment had a 22-fold greater likelihood of contracting the virus—despite not sharing syringes or needles—compared with those who did not share such equipment.

When PWID prepare drugs to inject, they use a metal cooker to dissolve drugs in water, followed by a filter to draw the resulting product, called the wash, into a syringe. Many of those interviewed for this study indicated they were injecting controlled-release hydromorphone, an opioid.

“Controlled-release hydromorphone is expensive and difficult to dissolve. After the first wash, large amounts of the drug remain in the equipment, which is then saved, shared or sold for future use,” Sharon Koivu, MD, an associate scientist at Lawson and associate professor at Schulich Medicine & Dentistry in London, Ontario, said in a press release. “While people know not to share needles, some use their own needle multiple times allowing for contamination of the equipment.”

Through laboratory experiments, the researchers found that on average, 45% of hydromorphone remains in the cooker following an initial wash. Additionally, HIV can travel between needles, cookers and filters. And crucially, properties of hydromorphone actually promote the virus’s survival.

“The slow release properties in the drug can unfortunately stabilize the HIV virus,” Eric Arts, PhD, chair of the department of microbiology and immunology at Schulich Medicine & Dentistry, said in the same press release. “For the first time, we were able to demonstrate that sharing equipment could lead to the type of HIV outbreak we observed in the community.”

Further tests indicated that holding a cigarette lighter under the cooker for about 10 seconds, or as long it takes for the wash to bubble, kills the virus without altering the concentration of the drug.

The investigators coined the phrase “cooking your wash” to describe this process and partnered with community organizations to promote the practice among PWID in London via a public healthcampaign. HIV rates then declined dramatically, although the study authors stress that the campaign was likely not the only factor that contributed to this turnaround, since other local interventions to mitigate HIV risk among local PWID were also introduced around this time.  

Previous studies have indicated that sharing injection-drug-use equipment facilitates hepatitis C virus (HCV) transmission. Additionally, controlled-release hydromorphone can promote the survival of bacteria that can lead to an infection of the heart valves known as endocarditis.

To read a press release about the study, click here.

To read the study abstract, click here.