The B.C. Centre for Excellence in HIV/AIDS tracked youth aged 14 to 26 over the course of six years.
Of 940 people recruited between September 2005 and November 2011, 100 tested positive for the disease at the outset.
Of the people 512 who tested negative at the beginning and showed up for at least one subsequent visit, 56 were positive in follow-up tests — 10.9 per cent.
And of those 512 youth, 166 — about 32 per cent — reported prior use of injection drugs.
"We found that the risk for (hepatitis C virus) acquisition among street youth in this setting was alarmingly high, and that intravenous drug injection remains a primary risk factor," said the study, led by Dr. Scott Hadland.
The study was also the first to look at the risk of hepatitis infection from injecting opioids like oxycodone and morphine, which is on the rise throughout North America.
It found that while the risk of infection is elevated by the injection use of heroin, cocaine and crystal meth, it does not appear to increase with opioid injection.
The researchers acknowledged that there was a relatively small number of youth in the study who engaged in prescription opioid misuse, which could have limited the ability to measure risk in opioid users.
It is also possible, the study said, that opioid users may not be as entrenched in the local drug scene and, therefore, may not associate frequently with hepatitis-positive drug users.
Either way, the excessive risk of infection among street youth requires specific prevention and mitigation strategies, the study found.
The street youth are a marginalized and difficult-to-reach population, Hadland wrote.
There are challenges to providing maintenance programs such as methadone to the population, and harm reduction services such as needle exchanges and safe injection sites may not effectively target younger users, he said in the study.