Hepatitis C

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

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 >/=20 years could increase substantially before peaking in 2015. If the incidence of new HCV infections does not increase in the future, persons born between 1940 and 1965 will be at highest lifetime risk of acquiring the infection.

Hepatitis C virus infection in the United States

Hepatitis C virus (HCV) infection is the most common chronic bloodborne infection in the United States, and most infected persons are younger than 50 years old. The relative importance of the two most common exposures associated with transmission of HCV, blood transfusion and intravenous drug use (IVDU), has changed over time. Blood transfusion, which accounted for a substantial proportion of HCV infections acquired >10 years ago, rarely accounts for recently acquired infections. In contrast, IVDU has consistently accounted for a substantial proportion of HCV infections and currently accounts for 60% of HCV transmission while sexual exposures account for up to 20%. Other known exposures (occupational, hemodialysis, household, perinatal) together account for about 10% of infections. In the remaining 10%, no recognized source of infection can be identified, although most persons in this category are associated with low socioeconomic level. Case-control studies have found no association with military service or exposures resulting from medical, surgical or dental procedures, tattooing, acupuncture, ear piercing or foreign travel. Reducing the burden of HCV infection and disease in the United States requires implementation of primary prevention activities that reduce or eliminate HCV transmission and secondary prevention activities that reduce liver and other chronic diseases in HCV-infected persons by identifying them and providing appropriate medical management and antiviral therapy. Surveillance and evaluation activities also are important to determine the effectiveness of these programs in reducing the incidence of disease, identifying persons infected with HCV, and promoting healthy lifestyles and behaviors.

The prevalence of hepatitis C virus infection in the United States, 1988 through 1994

BACKGROUND

Because many persons with chronic hepatitis C virus (HCV) infection are asymptomatic, population-based serologic studies are needed to estimate the prevalence of the infection and to develop and evaluate prevention efforts.

METHODS

We performed tests for antibody to HCV (anti-HCV) on serum samples from 21,241 persons six years old or older who participated in the third National Health and Nutrition Examination Survey, conducted during 1988 through 1994. We determined the prevalence of HCV RNA by means of nucleic acid amplification and the genotype by means of sequencing.

RESULTS

The overall prevalence of anti-HCV was 1.8 percent, corresponding to an estimated 3.9 million persons nationwide (95 percent confidence interval, 3.1 million to 4.8 million) with HCV infection. Sixty-five percent of the persons with HCV infection were 30 to 49 years old. Seventy-four percent were positive for HCV RNA, indicating that an estimated 2.7 million persons in the United States (95 percent confidence interval, 2.4 million to 3.0 million) were chronically infected, of whom 73.7 percent were infected with genotype 1 (56.7 percent with genotype 1a, and 17.0 percent with genotype 1b). Among subjects 17 to 59 years of age, the strongest factors independently associated with HCV infection were illegal drug use and high-risk sexual behavior. Other factors independently associated with infection included poverty, having had 12 or fewer years of education, and having been divorced or separated. Neither sex nor racial-ethnic group was independently associated with HCV infection.

CONCLUSIONS

In the United States, about 2.7 million persons are chronically infected with HCV. People who use illegal drugs or engage in high-risk sexual behavior account for most persons with HCV infection.

Agreement in pathologic interpretation of liver biopsy specimens in posttransplant hepatitis C infection

Hepatitis C virus-related disease is rapidly becoming the most common indication for orthotopic liver transplant (OLT) in the United States. Although post-OLT hepatitis C viremia is universal, 40% to 60% of patients develop recurrent chronic hepatitis C. Distinguishing recurrent chronic hepatitis C infection from acute rejection may be difficult because of overlapping histopathologic features. To improve our diagnostic accuracy we undertook a study to determine interobserver and intraobserver agreement between pathologists examining post-OLT liver biopsy specimens in patients from our transplant database. Clinical data and microscopic sections from 26 patients with hepatitis C virus-related OLT were reviewed. Biopsy specimens were obtained because of abnormal liver enzymes (21/26) or routine post-OLT follow-up (5/26), representing both early (18+/-11 days) and late (252+/-206 days) post-OLT periods. Unidentified sections were examined by an experienced pathologist in a randomly assigned order and reexamined 6 weeks later in the same fashion by the initial reviewer and a second experienced pathologist. Interobserver and intraobserver agreement was calculated using K statistic. The intraobserver agreement was 81 % with a kappa coefficient of 0.67 (P = .001). The interobserver agreement was 78% with a kappa coefficient of 0.60 (P < .001). The early post-OLT biopsy specimens (18+/-11 days) were the most difficult to interpret.

Hepatitis C

Hepatitis C virus (HCV) has emerged as a major cause of chronic liver disease worldwide. The widespread endemicity of HCV infection is the result of a combination of factors, including those related to the genetic diversity of the virus and the host response and those related to the specific settings and behaviors that have facilitated transmission. Most people who contract HCV infection become persistently infected, and the mechanism by which persistent infection is established seems to be related to the lack of development of an effective neutralizing immune response. The magnitude of the spread of HCV infection primarily is related to specific risk factors for transmission. The most important human behavior related to the transmission of HCV has been injection drug use, which in many developed countries has been the leading source of HCV infection during the past 20 to 30 years. The recognition of the clinical importance of HCV infection has resulted in a substantial amount of attention and resources rapidly directed toward developing new and improved therapies. The perception, however, of the public health importance of HCV infection is still limited. Despite the knowledge that injection drug use is the major source of HCV infection in the United States, this message has not been included in prevention and treatment programs, and the resources needed to support strong public health programs have yet to be identified.

The epidemiology of acute and chronic hepatitis C

Although the incidence of newly acquired acute hepatitis C virus (HCV) infection has declined, an estimated 3.9 million Americans are chronically infected with HCV, most of whom are young adults who will be at risk of the severe consequences of their infection in the next 10 to 20 years. The relative importance of the two most common exposures associated with the transmission of HCV has changed over time. Blood transfusions, which account for a substantial proportion of HCV infections acquired more than 10 years ago, account for only a small portion of recently acquired infections. In contrast, injection drug use has accounted for a substantial portion of HCV infections during both the remote and recent past. Sexual exposures, which have been poorly ascertained particularly among patients with chronic hepatitis C, may account for 10% to 20% of HCV transmissions. Physicians and other health care professionals need to be educated not only about the appropriate medical management of HCV infected patients, but also about the known and potential risks for HCV infection, the need to ascertain complete risk behavior histories from their patients, the appropriate evaluation of high-risk patients for evidence of infections, and the recommendations for prevention.