The past incidence of hepatitis C virus infection: Implications for the future burden of chronic liver disease in the United States

Abstract

Because chronic liver disease may develop many years after acute hepatitis C virus (HCV) infection, the past incidence of acute infections is a major determinant of the future burden of HCV-associated complications. We estimated past incidence of acute HCV infection using national seroprevalence data and relative age-specific incidence data from a sentinel counties surveillance system. Projections of the future prevalence of HCV-infected patients were derived from models that included an 85% drop in HCV infection incidence as observed for reported cases in the early 1990s. The models showed a large increase in the incidence of HCV infections from the late 1960s to the early 1980s. The degree of increase was dependent on the assumed rate of antibody loss; a model with 2.5% annual antibody loss showed annual incidence increasing from 45,000 infections (95% confidence interval [95% CI]: 0-110,000) in the early 1960s to 380,000 infections (95% CI: 250,000 to 500,000) in the 1980s. Projections showed that although the prevalence of HCV infection may be declining currently because of the decline in incidence in the 1990s, the number of persons infected for H20 years could increase substantially before peaking in Hepatitis C virus (HCV) infection is the most common chronic blood-borne infection in the United States and causes approximately 15% of all reported episodes of acute viral hepatitis. 1,2 Injection drug use and high-risk sexual activity are the most frequently identified risk factors associated with acute disease. Blood transfusion was a major risk factor for acquiring HCV infection before donor screening for human immunodeficiency virus infection, and surrogate marker testing for non-A, non-B hepatitis began in the mid-1980s, followed by screening for antibody to HCV (anti-HCV) in 1990. Young adults (ages 20 to 35 years) are at highest risk for acute infection, having an incidence 6 times higher than that of persons over 40 years 1 (Centers for Disease Control and Prevention [CDC], unpublished data).The most significant feature of HCV infection is the high rate of chronic infection and chronic hepatitis, which in the long term can lead to cirrhosis. 3 It is unknown how many of the nearly 4 million persons infected in the United States 2 will ultimately develop these complications.Direct determination of the incidence of new infections is impractical because most acute HCV infections are asymptomatic 4,5 and clinical disease is greatly under-reported. 6 In the past, the incidence of HCV infection has been estimated by adjusting the number of reported cases to account for under-reporting and for asymptomatic infections. An alternative method is to model incidence from prevalence data using ''catalytic modeling. '' 7,8 PATIENTS AND METHODSData Sources. The third National Health and Nutrition Examination Survey (NHANES III) was a cross-sectional national survey conducted from 1988 to 1994 that provided nationally representative prevalence estimates for a variety of health measures and conditions. 9 A total of...

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