In the old days, before 1989, doctors began seeing increasing numbers of a new liver infection, which they referred to as the somewhat benign-sounding hepatitis non-A non-B identifying it by what it wasn't rather than what it was.

Today, the ravaging effects of this blood-borne virus leave little doubt about what it is, and it is far from benign. Now known as hepatitis C, this virus is emerging in epidemic proportions. It is the leading reason for liver transplants in the United States, causes up to 50 percent of liver cancer cases and contributes to the deaths of up to 10,000 people per year.

Four times as many people in the United States are infected with the hepatitis C virus-four million peoplethan are infected with HIV, according to the Centers for Disease Control and Prevention (CDC). Each year, another 30,000 people are newly infected. The major hazard of the hepatitis C virus is its likelihood of developing into chronic viral hepatitis C. This happens in more than three-quarters of those who test positive for the virus.

AT-RISK GROUPS. The disease affects the liver—hepatitis means inflammation of the liver—but generally causes no symptoms for several decades after an individual has been infected. It silently works its way into the liver, causing irreversible damage without sending any sort of signal until usually it is too late. In the early stages, patients may experience such nonspecific symptoms as fatigue and malaise. Liver enzyme levels (ALT or alanine transferease) may be elevated. A liver biopsy may show some inflammation. Left untreated, the virus can go on to cause further damage in the form of cirrhosis (scarring), cancer and liver-function complications.

Early testing for those at risk can help avoid liver deterioration. Testing is recommended for anyone who received blood transfusions or organ transplants prior to July 1992 (after this time, universal testing of the blood supply was initiated), those who shared needles to inject drugs, healthcare workers exposed to blood or who experienced needle-sticks, anyone who received blood-clotting factor concentrates before 1987, and those who had longterm kidney dialysis. Other potential risks may include: sex with multiple partners, tattooing or body piercing with shared needles or unsterilized equipment, and intranasal cocaine use with shared straws.

The current situation is only the tip of the iceberg. The number of deaths from hepatitis C is expected to triple in the next 10 to 20 years and, according to a recent analysis by healthcare actuaries, the cumulative death toll could reach close to half a million by the year 2020.

THE "CURE"? Unlike its sister diseases-the A and B forms-hepatitis C has no vaccine. However, for those infected, treatments are available that can help reduce the toll of the disease. A combination of the antiviral drugs interferon and ribavirin reduces the virus to undetectable levels in about 40 percent of patients. When the virus remains undetectable after treatment is stopped, many physicians consider it a true "cure." Most people, however, don't understand that this is possible.

Public-education programs are now trying to track down cases of hepatitis C in the hope that early testing and treatment will reduce suffering and death. Recently, the CDC sent letters to individuals who had blood transfusions that may have been contaminated with hepatitis C. And although anyone with known risk factors can be infected, certain at-risk demographic groups are targeted for additional outreach. They include war veterans (especially from the Vietnam era), Hispanic Americans, African Americans and prison inmates. In addition, the U.S. Public Health Service has recently named hepatitis C an official opportunistic infection of HIV. Now that HIV patients are living longer, hepatitis C is becoming a major cause of death among those with AIDS.

The bottom line is that if infected individuals are not treated early, the epidemic will prove to be very costly to the nation-in lives and quality of life.

Dr. Dieterich is president and chairman, Hepatitis Resource Network, as well as chief, Division of Gastroenterology and Hepatology, Cabrini Medical Center, and clinical associate professor of medicine, Department of Medicine, at the New York University School of Medicine, both in New York City.