Scientists isolated and sequenced the hepatitis C virus (HCV) genome 10 years ago. This led to the development of diagnostic tests to identify people infected with HCV. Almost 4 million people in the United States, or 1.8 percent, are persistently infected, and the Institute of Medicine now includes hepatitis C virus in its list of emerging infectious diseases.

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Those with the greatest risk of infection are individuals who ever experimented with injection drugs, even once or twice in the distant past, had multiple sexual partners, or received blood or blood products, for example, a transfusion prior to 1992.

HCV damages the liver, one of the body's most important organs. Symptoms of both acute and chronic infections are easily confused with less serious and shorter-term illnesses. In fact, most infected people are relatively free of physical symptoms -- signs of liver damage may not occur for a couple of decades. Unfortunately, by the time the disease becomes apparent, liver damage can be considerable and even irreversible.

HCV is not related to the other hepatitis viruses (A-E) and diagnostic tests readily distinguish them. The virus is usually detected by an antibody test. Unlike many other infections, the presence of antibodies in the blood does not mean recovery. Although rare, recovery does occur; it can be confirmed using highly sensitive diagnostic tests that detect the viral genome (RNA). Unfortunately, such tests are not yet licensed and there is laboratory variability.

Roughly 50 percent of chronic carriers do not even know they have hepatitis C, a disease that moves through specific stages of liver damage. Currently, diagnosis of the stage requires a liver biopsy, i.e., removal of a very small piece of the liver, and evaluation of an even smaller piece using a microscope. The rate of progression is highly individual and can be characterized as slow, medium or fast.

For most people it is slow, i.e., after 20 years of chronic infection, only 20 percent of individuals progress to cirrhosis. Alcohol and other hepatitis viruses hasten progression of the disease. Thus, if they know they are infected, individuals can help themselves by not using alcohol, and by getting vaccinated to prevent hepatitis A and B.

The Food and Drug Administration (FDA) has approved treatments that can get rid of the virus and make the liver more normal. Three are interferons and the fourth combines interferon and ribavirin. Unfortunately, none of these drugs is very effective (approximately 5 percent of infections are eradicated with interferons and 35 percent with the combination) and all have significant side effects.

Currently, there is no way to predict who will or won't respond. However, the best responses are seen in those patients with HCV variants (genotypes) 2 and 3, less severe fibrosis, and who are female or are under the age of 40 years. It is important to note that genotype 1, which predominates in this country, is least responsive to treatment.

The fact that most people lack symptoms and may have been infected years earlier, taken together with the drugs now available to treat the disease, make it important for individuals to report accurate personal histories to their physicians so that detection and treatment of hepatitis C begins as early as possible.

Hepatitis C virus infection is an increasing public health concern. Without more effective therapies that produce recovery, the Centers for Disease Control and Prevention (CDC) predicts that deaths due to HCV will double or triple in the next 15 to 20 years due simply to the length of time most people in the United States have been infected.

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