Hepatitis C: controversies, strategies and challenges.

Risk factors for hepatitis C infection include I.V. drug use (42%); history of blood transfusion (6%); exposure to multiple heterosexual partners (6%); exposure to a household contact (3%); health care employment (2%); or hemodialysis (1%). Forty percent of patients have no identifiable risk factors. The HCV is a single-stranded, positive-sense RNA virus. Six major genotypes have been identified; each contains a series of subtypes. In the U.S., prevalences are type 1 (74%); type 2 (15%); type 3 (6%); and type 4 (1%). Within an infected individual, HCV also exists as a spectrum of closely related genotypes referred to as a quasispecies, and more complex quasispecies correlate with longer duration of disease, higher levels of viremia, genotype 1 infection, and poorer response to interferon therapy. Diagnosis is made by measuring anti-HCV by EIA, with confirmation by RIBA or HCV RNA. Patients with chronic HCV infection, with or without aminotransferase elevation, have detectable serum RNA by PCR. Standard therapy is interferon alfa 2b (Intron A) at a dosage of 3 million units 3 times a week for 6 months. This results in a 40%-50% complete response at the end of treatment (normal aminotransferases and undetectable HCV RNA), but relapse occurs in 60%-80% of cases over the next six months. Longer (12 month to 18 month) courses are now widely advocated. Better patient selection, e.g., those with low serum HCV RNA levels and absence of cirrhosis, and increased duration of therapy may lead to better response rates. Combination therapy with other antiviral agents, such as ribavirin, has dramatically reduced relapse rates.