Florida ? Doctors and researchers almost never use the word “cure,” but they came as close as they ever do Monday when describing a combination of two drugs used to treat the severe liver disease hepatitis C.

Among some patients, the drug cocktail of pegylated interferon and ribavirin completely kills the virus that causes hepatitis C and keeps it from coming back, doctors said in reporting their new study at a Digestive Disease Weekly conference in Washington, D.C.

The catch is, the drug combo does not work in about half of people with hepatitis C, and researchers still are not sure why it works so completely for some but fails in others. Also, the combo has difficult side effects.

“I call it a cure. It doesn’t work for everyone but it has the ability to eradicate this virus, and this study is the best evidence to prove that,” said Dr. Eugene Schiff, director of the center for liver diseases at the University of Miami medical school, who was attending the conference but not involved in the study.