One example is Scott County, Indiana, where 215 people were diagnosed with HIV between 2011 and 2015, according to a 2018 Lancet study. Koeppel said 36% of drug users they’ve tested in Appalachian Virginia have hepatitis C. Nationally, a CDC estimate says 1% of the U.S. population has hepatitis C. A 2018 UVA study found links between rising injection drug use and endocarditis, an infection of the heart chamber lining.