Hepatitis C

Abstract

Hepatitis C virus (HCV) is the most common chronic viral infection in North America and Europe and a common infection worldwide. In the United States Third National Health and Nutrition Examination Survey, it was estimated that 3.9 million people had detectable antibodies to HCV, and 75% of them were positive for HCV RNA (1). This survey included only individuals living in households. There is evidence that HCV is much more common in certain populations, such as the homeless and prison inmates, where prevalence might be as high as 40% (2). The prevalence of HCV is also higher among veterans seeking care in VA medical centers; nationwide, the prevalence is just under 7% (3), with a prevalence over 10% in urban hospitals (4). Worldwide, an estimated 170 million individuals are chronically infected with HCV (5). The age of infected individuals differs significantly in different areas of the world. In Australia, North America, and much of Europe, infections seems to peak in persons currently between the ages of 40 and 60, whereas in Japan, Italy, and Egypt, prevalence of HCV infection increases steadily with increasing age (6). Males are more likely to be infected than females (1). The prevalence of acute infections with HCV has fallen by 80% over the past decade (7).

There are a number of recognized risk factors for HCV. The most common are injection drug use and transfusion or transplantation before 1992 (8). Although the overwhelming majority of those using injection drugs in the 1960s and 1970s became infected with HCV (9), the likelihood of infection among current, younger injecting drug users is only about 50% (10), this reflects an overall decline in the incidence of acute HCV infection among injecting drug users (7). Even among blood donors who initially deny risk factors but are found to be HCV positive, a history of injection drug use on follow-up questioning is 50 times more likely than in donors who are HCV negative (11). Less commonly, HCV is transmitted by dialysis(12,13), by needle-stick injury (14), and by vertical transmission from an infected mother to her child (15–17); the likelihood of infection with the last two of these routes is approx 3–5%. The role of sexual transmission is controversial, but evidence suggests that having multiple sexual partners increases risk of transmission of HCV (18–21); the likelihood of infection in monogamous sex partners of HCV-infected individuals is similar to that in the population as a whole, however (22,23).