The incidence of hepatitis C virus (HCV) infection increased markedly in the 1970s and 1980s. These increases were mainly attributable to blood transfusions and injection drug use. 1,2 The blood supply was not screened for HCV before 1992 (now, HCV infection by blood transfusion is rare). 2,3 Surveillance of the period 1992-2003 showed a substantial decrease in the incidence of acute hepatitis C cases, and the rate remained steady through 2010. 2,3 Over the past 5 years, HCV has returned to national attention with a rising infection rate (2.5-fold increase during 2010-2013) and a rapid succession of FDA approvals of direct-acting antiviral agents (DAAs). 4 Currently, the most prevalent mode of infection is injection drug use, accounting for > 50% of all cases of HCV infection and 84% of acute HCV infections. 5
Baby boomers (people born between 1945 and 1965) account for three-fourths of the population currently living with chronic HCV infection resulting from past infection. 6 Historically, rates of acute and chronic infection have been far higher for blacks than for whites and Hispanics. 2,4,7,8 In 2004, that trend started to reverse, with the incidence in whites surpassing that in blacks. 4 Recent reports have identified a new cohort of HCV-infected injection drug users (IDUs) who are young (aged ≤ 24 years) and white nonurban dwellers. 5
HCV Infection Among High Risk Individuals
In the U.S., unlike in other parts of the world, HCV infection is more prevalent than hepatitis B virus (HBV) infection. 4,9,10 According to the National Health and Nutrition Examination Survey (NHANES), about 2.7 million Americans have chronic HCV infection. However, NHANES surveys do not sample certain populations, including the incarcerated and the homeless, in whom infection rates are thought to be higher. 11 The incarcerated, the largest institutionalized group, have the highest incidence: One in 3 is infected with HCV. 12 This rate is attributable to high rates of injection drug use and other high-risk behaviors. Drug-related offenses account for 50% of federal prison incarceration. 13 For IDUs, the HCV infection rate is as high as 70% to 90%. Despite widespread implementation of needle-exchange programs after the discovery of HIV in the 1980s, recent surveys have indicated that about one-third of 18- to 30-year-old active IDUs are infected with HCV. 14
Penitentiary Inmates Infected With HCV
A 2015 search of the Federal Bureau of Prisons (BOP) electronic medical records at the U.S. Penitentiary Canaan (USP Canaan) found that out of a population of about 1,600 inmates, 182 (11%) had tested positive for HCV antibodies (anti-HCV). This percentage likely is an underestimation, because HCV testing is not mandatory, and many (45%-85%) of the infected are unaware of their HCV infection status. 2 Most of the infected remain chronically infected and are not being treated.
Prevalence of HCV infection commonly refers to chronic HCV infection. The diagnosis of chronic HCV infection is established by presence of HCV RNA on polymerase chain reaction assays. Of the 182 inmates who tested positive for anti-HCV, 45 had their cases resolved (undetectable HCV RNA), 34 spontaneously, and the other 11 after treatment, primarily with peginterferon and ribavirin (pegINF/RBV) dual therapies. The remaining 137 who tested positive remained chronically infected. This chronically infected group represented 9% of the population of 1,600 inmates. Although the infection rate is significantly higher than that in the general population (1% incidence), the inmates’ true rate of infection in all probability is much higher. 11