Hepatitis C Infection in the United States

Hepatitis C virus (HCV) infection is the most common chronic bloodborne viral infection in the United States. First identified in 1988, HCV is the causative agent for what was formerly known as non-A non-B hepatitis, and is estimated to have infected as many as 242,000 Americans annually during the 1980's. Since 1989, the annual number of new infections has declined by more than 80 percent to approximately 41,000 by 1998. A national survey (the third National Health and Nutrition Examination Survey [NHANES III]) of the civilian, non-institutionalized U.S. population found that 1.8 percent of Americans (3.9 million) have been infected with HCV, of whom most (2.7 million) are chronically infected with HCV.

These estimates of prevalence are likely conservative, because the survey excluded incarcerated and homeless persons, groups that have high prevalence of HCV infection. Most infected persons were aged 30-49 years when the survey was done in the early 1990s (Figure 1).

 Prior to the mid-1980's there was a 7 percent to 10 percent risk of non-A, non-B hepatitis (hepatitis C) from blood transfusion. This risk declined by more than 50 percent between 1985 and 1990 as a result of implementation of blood donor screening for HIV and surrogate testing for non-A, non-B hepatitis. In 1990, specific donor screening for HCV was implemented and by 1992 the risk of HCV infection from a unit of transfused blood was reduced to one in 100,000. As of 2001, the risk of HCV infection from a unit of transfused blood is less than one per million transfused units.

Clotting factor concentrates, which are plasma-derived products used to treat individuals with hemophilia, posed a high risk for HCV infection prior to the use of virus inactivation procedures that were introduced in 1985 and 1987. Except for one outbreak of hepatitis C from a single type of contaminated intravenous immunoglobulin, other plasma-derived products, including immune globulin for intramuscular administration, have not been associated with the transmission of HCV in the United States. Currently, all immune globulin products undergo a virus inactivation procedure or test negative for HCV prior to release.

Sexual exposures account for about 15 percent of cases of hepatitis C. Although the risk for transmitting HCV infection through sexual intercourse is low, sex is a common behavior in the general population, a substantial proportion of the adult population has had unprotected sex with multiple partners, and there are a large number of persons with HCV infection. While other types of exposures are more likely to transmit HCV (e.g., transfusion from an infected donor), they account for a smaller proportion of infections because of the relatively small proportion of the population in whom these exposures have occurred.

Exposures resulting from hemodialysis, employment in the health care field, and birth to an HCV-infected mother together account for about 5 percent of cases. About 10 percent of people with HCV infection have no recognized source for their infection.

While it is possible for HCV to be transmitted from any percutaneous exposure to blood, exposures such as tattooing, body piercing, or acupuncture have not been shown to place people at increased risk for infection. Higher rates of HCV infection are not found among persons with these exposures alone and these exposures are rarely reported among new cases of hepatitis C.

Consequences of HCV infection.  About 15 percent to 25 percent of persons with acute hepatitis C resolve their infection without further problems. The remainder develop a chronic infection and about 60 percent to 70 percent of these persons develop chronic hepatitis. Cirrhosis of the liver develops in 10 percent to 20 percent of persons with chronic hepatitis C over a period of 20-30 years, and hepatocellular carcinoma (liver cancer) in 1 percent to 5 percent. For individuals with cirrhosis, however, the rate of development of liver cancer might be as high as 1 percent to 4 percent per year.

Lower rates of complications have been reported from studies of persons who acquired infection as children. However, longer term follow-up studies are needed to assess lifetime consequences of chronic HCV infection in different populations, especially among children.

Chronic liver disease is the tenth leading cause of death among adults in the United States. It is estimated that 40 percent to 60 percent of chronic liver disease is due to hepatitis C and another 10 percent to 15 percent is due to chronic hepatitis B. HCV-associated chronic liver disease is the most frequent indication for liver transplantation among adults. Additionally, because alcohol use is one of the most important contributing factors to progression of chronic liver disease among persons with hepatitis C, it is important to identify infected individuals as early as possible so that they can be counseled to limit alcohol consumption and be offered treatment if appropriate.

Treatment for hepatitis C. In 1997, an NIH Consensus Development Conference established guidelines for the medical management of hepatitis C¹ ,which have since been updated to reflect the evolving nature of antiviral therapy. A combination of alpha-interferon and ribavirin currently is the most effective therapy and achieves the sustained elimination of HCV infection for at least 6 months in 30 percent to 40 percent of patients.

However, 10 percent to 20 percent of treated patients do not complete therapy because they experience significant side effects. In addition, some patients may have conditions, such as severe cirrhosis which prohibit treatment. Current antiviral therapy is not licensed for patients below age 18 years.

Persons with chronic hepatitis C who continue to abuse alcohol are at risk for ongoing liver injury and antiviral therapy may be ineffective. In addition, interferon therapy can be associated with relapse in people with a previous history of alcohol abuse; therefore, abstinence from alcohol is recommended during antiviral therapy. Interferon therapy should be considered with caution for patients who recently stopped alcohol abuse, and these patients require the support of alcohol treatment programs.

Patients with hepatitis C on methadone treatment have been successfully treated with interferon. However, there is limited experience with treatment of persons who are recovered injection drug users or who are active injection drug users. In addition, there is the concern that active injection drug users are at risk for re-infection with HCV. When patients with past or continuing substance abuse are considered for antiviral treatment, such patients should receive drug treatment or care from substance abuse specialists or counselors.

Persons with HCV-related liver disease should be vaccinated against diseases that may produce further complications or increase their risk of death. Susceptible persons with chronic liver disease should receive hepatitis A vaccine since they are at increased risk of death from liver failure if they get hepatitis A. All persons with chronic liver disease should be vaccinated annually against influenza and should receive pneumoccocal vaccine. In addition, persons with continued risk factors for HBV infection should receive hepatitis B vaccine.

Co-infection. Coinfection with HCV, HIV and/or HBV is currently recognized as a serious problem and is more likely to be found among injection drug users and persons treated for hemophilia before the availability of inactivated clotting factor concentrates. Deaths from chronic hepatitis C among patients with HIV are expected to increase as advances with antiretroviral therapy extend the life span of these patients. Management of HIV infection in HCV co-infected patients generally is similar to that for patients with HIV alone, although there is some risk of liver toxicity from the antiretroviral drugs. HCV co-infected patients should be evaluated to determine if they are candidates for antiviral treatment of their chronic liver disease. Because treatment and medical management of co-infected patients is complicated and rapidly evolving, such patients are best managed by health care providers with experience in treating both HIV and HCV infection. More research is needed to determine the ideal management and treatment of co-infected individuals.