Counterattack

When it comes to hepatitis, doctors, like children, must learn their ABCs. As they have long been taught, the liver-destroying disease is caused by two distinct viruses, known as A and B. But many patients show no signs of having been exposed to either virus. Earlier this year scientists took a significant step toward solving the riddle of non-A, non-B hepatitis by moving on down the alphabet. They identified a third virus that produces hepatitis and called it type C. Last week researchers announced another milestone: the first effective therapy for hepatitis C.

Reporting in the New England Journal of Medicine, two separate teams of scientists found that treatment with the drug interferon halted destruction of liver cells in about half the patients with chronic hepatitis. A total of 207 people were studied by the two teams, one led by investigators at the University of Florida, the other at the National Institute of Diabetes, Digestive and Kidney Diseases.

Patients received injections of interferon, a natural infection-fighting protein that can be artificially produced by genetically altered bacteria. One drawback: most of the patients who improved suffered a relapse when the injections ended. Doctors think the problem may be resolved by giving interferon for longer periods or in higher doses. Says Dr. Saul Krugman of New York University medical school: "There's no question that it is very promising."

Hepatitis C afflicts an estimated 150,000 Americans each year. The virus, like type B, is spread primarily by sexual activity and through tainted blood in transfusions or on addicts' dirty needles. (Hepatitis A is passed along mainly through contaminated foods.) Researchers at Chiron Corp., a biotechnology firm in Emeryville, Calif., that first identified the C virus, have devised a test for the pathogen that can be used to screen the blood supply.

Many of the people who contract hepatitis C never show symptoms. But like Typhoid Mary, they become silent carriers of the disease. About half those infected eventually suffer liver damage. Some 15,000 patients a year develop cirrhosis, and a small number may get cancer. That toll may be cut by interferon. But doctors warn that the mystery of non-A, non-B hepatitis may not be completely resolved. Type C virus could account for most of these cases, but there is evidence that yet another blood-borne virus will extend the hepatitis alphabet still further.