HEPATITIS C - A SILENT EPIDEMIC
The estimated number of new hepatitis C virus (HCV) infections annually in the United States is approximately 150,000 although the true incidence is probably greater. Screening of healthy blood donors indicates that the minimum prevalence of chronic HCV infection is 1 per 200 in this low-risk population. The true prevalence may be closer to 1.0 - 1.5%. An estimated 3 - 3.5 million Americans are carriers of the hapatitis C virus.
Transmission of Virus:
Transfusion of blood products used to be the primary source of transmission of the virus. Use of volunteer donors and screening of blood for the antibody to the virus has reduced the risk of acquiring hepatitis C from a transfusion to 1 per every 3000 units of transfused blood. Currently only 4% of patients with chronic HCV acquire the infection by blood transfusion, hence screening of transfused blood for HCV contamination is unlikely to reduce the prevalence of chronic HCV.
Thirty-eight percernt of chronic HCV infections are due to intravenous drug use, 1% are dialysis patients, 10% are patients with a history of sexual contacts or a household contact with someone with hepatitis C. Although 30 - 45% of infected patients deny any discernible risk factors for the disease, many of these individuals have histories of high risk behaviors such as multiple sexual partners, illicit non-intravenous drug use or prior imprisonment.
Hepatitis C is a known occupational hazard. Two percent of cases of hepatitis C are due to occupational percutaneous exposures, mostly in the form of needle sticks in health-care workers. The risk of acquiring the virus from a single needle stick from an infected individual is estimated to be approximately 10%. There have been numerous studies of the prevalence of hepatitis C in different health-care populations. Some groups such as oral surgeons who are often exposed to aerosolized blood may have a prevalence of HCV as high as 10%, 4 - 6 times the national average. Dialysis and operating-room nurses are higher risk than non-surgical hospital personnel with prevalences ranging from 1.5 to 4%.
The majority of infections with HCV are clinically silent. The infected individual may have no symptoms for 30 - 40 years. The infection is often discovered accidentally during routine physical examinations or during applicaitons for life insurance. The disease will occasionally present as new-onset liver failure or liver cancer.
The natural history of chronic HCV disease is still being defined. The virus has only been identified and sequenced within the last four years. It is generally accepted that 20 - 30% of patients with chronic HCV will progress to cirrhosis (scarring and malfunction of the liver), and liver cancer develops in about one fifth of patients with cirrhosis. The slowly progressive nature of this disease is apparent from a retrospective study of post-transfusion HCV showing that chronic hepatitis, cirrhosis and liver cancer developed after a mean of 10, 21 and 29 years respectively. Once cirrhosis develops the risk of liver cancer is from 3 - 6% per year. HCV accounts for 25% of patients undergoing liver transplantation.
The best current data suggest that the risk of developing clinical liver failure is 5 - 15% and the risk of dying from liver-related complications 3 - 9%. Conversely, 80 - 90% of infected individuals will probably live normal life spans without symptomatic liver disease.
Can HCV Infection be Treated?
The goad of anti-hepatitis C therapy is to ameliorate symptoms and halt the progression of disease to cirrhosis and possible liver cancer. Alpha2b-Interferon was licensed for the treatment of chronic hepatitis C in 1991. It is the only agent which has shown efficacy against the virus. Although 40 - 50% of patients respond to a 6 month course of treatment with normalization of liver enzyme levels, the relapse rate after therapy is at least 50% and as high as 80%. Unfortunately, three to four years after successful interferon treatment only 8 - 15% remain free of virus and have normal liver function tests.
Interferon therapy is associated with considerable morbidity. It must be administered subcutaneously. At the beginning of therapy 60 - 80% of
patients have a flu-like illness which resolves within three weeks. Additional side-effects include irritability, fatigue, depression, anorexia, nausea, rashes and hair loss. Migraine headaches may increase in severity and frequency. A history of anxiety or depressive illness is a relative contraindication to interferon treatment.
At current Food and Drug Administration approved dosing 85 - 92% of treated patients will not ultimately benefit from interferon treatment. Since the best current estimates are that clinically significant disease will occur in only 5 - 15% of infected individuals, the vast majority of infected individuals will not benefit from interferon therapy. Assuming a "cure" rate of 8 - 15% in the 5 - 15% who would potentially benefit from treatment, one comes to an estimated improvement in outcome in only 0.4 - 2.25% of patients. Even this higher number is doubtful since the group with the most aggressive disease tends to have the lowest response to interferon.
Recent studies indicate that a mere six months of treatment at three million units may be suboptimal. Treatment with high doses (up to 30 million units per week) for 12 - 18 months have produced "cures" in 22 - 45%. To get sustained remission in over 50% of patients on a consistent basis may require several years of interferon therapy.
In summary HCV infection is a serious viral epidemic affecting 1.5% of the United States population. Health-care personnel are at risk for occupational exposure, especially those exposed to blood products on a regular basis such as dialysis and operating room nurses. Although treatment is available it is associated with considerable expense and morbidity and fails to cure the disease in up to 90%. The infection can lead to liver failure and liver cancer in a substantial minority of infected individuals. The disease is becoming an important issue in workers compensation for health-care employees. Extensive research is underway in an attempt to develop more effective therapies.