Injection drug use is a known risk factor for transmission of the hepatitis C virus (HCV), but a new study published in Epidemiology and Infection shows that intranasal drug use and incarceration may be independent risk factors for HCV infection as well.
“Our study is one of the first to implicate intranasal drug use and incarceration as independent indicators of risk for HCV transmission,” said lead author Mary-Margaret Fill, MD, medical epidemiologist, Communicable and Environmental Diseases and Emergency Preparedness, Tennessee Department of Health, Nashville, TN.
“While these risk factors may be indicators of other high-risk behaviors, such as injection drug use, our findings suggest that persons who report a history of using intranasal drugs and persons with a history of incarceration are important to consider in HCV prevention and testing strategies,” Dr. Fill added.
The most common intranasal drugs reported in the study were heroin, opioids, cocaine, methamphetamine, and benzodiazepines.
Epidemic in Appalachia
Baby boomers account for more than 75% of chronic HCV infections in the United States, but most new infections occur in younger Americans. In Tennessee and other Appalachian states, acute HCV infections among people aged 30 and younger have skyrocketed—up 364% between 2006 and 2012, with more than 70% reporting injection drug use, according to the Centers for Disease Control and Prevention (CDC).
More recently, the rate of newly reported chronic HCV cases in Tennessee increased more than 400%, from 63 cases/100,000 persons in 2013 to 317 cases/100,000 in 2016. Numbers were even higher in eastern Tennessee, with 489.5 cases/100,000 in 2016.
“We’ve seen a significant rise in acute and chronic cases of hepatitis C virus in Tennessee over the last several years,” Dr. Fill said. “[We] completed this analysis to better understand what behaviors may be driving this increase, as well as to identify potential opportunities for intervention.”
For this study, Dr. Fill and colleagues at the Tennessee Department of Health and the CDC performed HCV testing and risk factor assessment in sexually transmitted disease (STD) clinics, family planning clinics, and an addiction treatment facility in eastern Tennessee from June to October 2016.
Testing and prevention
Of 4,753 people tested, 8.4% were found to be HCV positive (average age 37.3 years). About 9% of those tested reported a history of injection drug use, and 20% reported a history of intranasal drug use. More than 25% of the overall study population and more than 75% of those who tested HCV positive reported a history of incarceration longer than 24 hours.
“Our findings indicate that after adjusting for sex, race, testing location, clinic type, and other risk factors, injection drug use, intranasal drug use, and incarceration are independent indicators of risk for past or present HCV infection within the study population,” the authors wrote.
Dr. Fill added, “Since our study was conducted only within Tennessee, it’s impossible to generalize our findings to other parts of the country; however, it’s certainly possible that other areas may have similar findings.”
The researchers also found that intranasal drug use often preceded injection drug use by a median of 5.5 years, and that a higher proportion of HCV-positive people reported sharing drug-snorting utensils.
“This delay before the development of riskier drug use behaviors might be an opportunity for public health intervention that warrants exploration,” the authors wrote. “If this is a common trend, it offers important information that may be applicable to public health prevention programs.”
Identifying intranasal drug use and incarceration as independent risk factors for HCV could lead to new avenues to find more people who are infected. For example: “The prevalence of [HCV-positive] persons among STD clinic patients was approximately 10%, suggesting there may be utility in incorporating HCV testing into routine STD assessment,” the researchers noted.