Opioid tampering by health care providers is the biggest contributor in the developed world to hepatitis C virus (HCV) infections related to health care, according to a new study from the U.S. Centers for Disease Control and Prevention (CDC) and reported by Healio.com.

For the study, published in the journal Hepatology, CDC researchers created a new risk-assessment model that compiled data from 46 different health care-related HCV outbreaks in developed countries between 1990 and 2012. The model was employed to compare the risks of provider-to-patient hep C transmission via several different means.

Out of all the outbreaks investigated, CDC analysts found that eight were due to doctors tampering with opioid anesthetics, seven were due to surgeries, seven were caused by anesthesia provision and 24 were caused by health care workers breaching infection control strategies.

Researchers also found that tampering was associated with 17 percent of all health care-related HCV outbreaks, as well as 53 percent of total hep C cases over time. Of those, 75 percent involved the opioid anesthetic fentanyl. What’s more, 63 percent of tampering-related hep C outbreaks happened in the United States.

Transmission risk was highest among providers who had an unknown HCV status. Findings also showed that opioid tampering was 135 times more risky in terms of hep C infection than receiving surgery from a provider who was HCV positive.

Based on these findings, the CDC strongly recommends that health care staff raise awareness about provider substance abuse and treatment options, and highlight the importance of screening health workers for opioid addiction and hep C.

The report also recommends that hospitals and doctors offices across the country employ computerized dispensing and charting systems to monitor the amount of drugs being administered at their facilities, as well as filing complete criminal and background checks for all health care professionals.