Background Knowledge of the number of persons with chronic hepatitis C virus (HCV) infection in the United States is critical for public health and policy planning. Objective To estimate the prevalence of chronic HCV infection between 2003 and 2010 and to identify factors associated with this condition. Design Nationally representative household survey. Setting U.S. noninstitutionalized civilian population. Participants 30 074 NHANES (National Health and Nutrition Examination Survey) participants between 2003 and 2010. Measurements Interviews to ascertain demographic characteristics and possible risks and exposures for HCV infection. Serum samples from participants aged 6 years or older were tested for antibody to HCV; if results were positive or indeterminate, the samples were tested for HCV RNA, which indicates current chronic infection. Results Based on 273 participants who tested positive for HCV RNA, the estimated prevalence of HCV infection was 1.0% (95% CI, 0.8% to 1.2%), corresponding to 2.7 million chronically infected persons (CI, 2.2 to 3.2 million persons) in the U.S. noninstitutionalized civilian population. Infected persons were more likely to be aged 40 to 59 years, male, and non-Hispanic black and to have less education and lower family income. Factors significantly associated with chronic HCV infection were illicit drug use (including injection drugs) and receipt of a blood transfusion before 1992; 49% of persons with HCV infection did not report either risk factor. Limitation Incarcerated and homeless persons were not surveyed. Conclusion This analysis estimated that approximately 2.7 million U.S. residents in the population sampled by NHANES have chronic HCV infection, about 500 000 fewer than estimated in a similar analysis between 1999 and 2002. These data underscore the urgency of identifying the millions of persons who remain infected and linking them to appropriate care and treatment. Primary Funding Source None.

Many persons infected with hepatitis C virus (HCV) are unknown to the healthcare system because they may be asymptomatic for years, have not been tested for HCV infection, and only seek medical care when they develop liver-related complications. We analyzed data from persons who tested positive for past or current HCV infection during participation in the National Health and Nutrition Examination Survey (NHANES) from 2001 through 2008. A follow-up survey was conducted 6 months after examination to determine (1) how many participants testing positive for HCV infection were aware of their HCV status before being notified by NHANES, (2) what actions participants took after becoming aware of their first positive test, and (3) participants' knowledge about hepatitis C. Of 30,140 participants tested, 393 (1.3%) had evidence of past or current HCV infection and 170 (43%) could be contacted during the follow-up survey and interviewed. Only 49.7% were aware of their positive HCV infection status before being notified by NHANES, and only 3.7% of these respondents reported that they had first been tested for HCV because they or their doctor thought they were at risk for infection. Overall, 85.4% had heard of hepatitis C; correct responses to questions about hepatitis C were higher among persons 40–59 years of age, white non-Hispanics, and respondents who saw a physician after their first positive HCV test. Eighty percent of respondents indicated they had seen a doctor about their first positive HCV test result. Conclusion: These data indicate that fewer than half of those infected with HCV may be aware of their infection. The findings suggest that more intensive efforts are needed to identify and test persons at risk for HCV infection.

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