A new study finds rates of heroin use, injection and addiction increased steadily between 2008 and 2016, Reuters reports. The increase may help explain the rising rates of hepatitis C, the researchers say.

Heroin use increased by an average of 7.5% each year between 2008 and 2016, the researchers found. There were similar increases in heroin injection and addiction rates during that period, they report in JAMA. Rates leveled off or decreased slightly after 2016, they found.

Study coauthor Dr. Nora Volkow, Director of the National Institute on Drug Abuse, noted that hepatitis C is spread through the sharing of needles and syringes by multiple people. Rates of hepatitis C infections climbed sharply starting around 2010, particularly in people ages 20-39.

“The problem is there are many places where access to clean syringes and needles is not available,” Volkow said. “What we’re seeing highlights the gap between what evidence-based practice tells us about how to protect against hepatitis C infection and what we are doing.”