Scientists have found a way to prevent lasting liver damage in patients with the potentially deadly infection hepatitis C.

However, the drug treatment only works if it is administered during the earliest stages of the disease.

The breakthrough could affect the treatments of millions of people who have been infected with the virus.

A team led by Dr Elmar Jaeckel, of the Hanover Medical University in Hanover, Germany, were able to prevent the development of chronic hepatitis C in 44 volunteers suffering from the acute, short-term version of the illness.

In all but one case, daily injections of the drug interferon alfa-2b reduced the amount of hepatitis C virus (HCV) in the blood to undetectable levels.

The current treatment for chronic HCV infection eliminates the virus in only about half the cases

The researchers believe that everybody with acute hepatitis C should receive interferon

Researcher Dr Michael Manns said that now they had shown that the development of long-term disease could be prevented, it was more important than ever that doctors diagnosed acute hepatitis C in its earliest stages.

He said: "Everyone should be alert to diagnosing acute hepatitis C."

Common infection

Nearly 170 million worldwide are believed to be infected with the hepatitis C virus. Long-term infection is a leading cause of liver disease and can lead to total organ failure.

Hepatitis C usually comes from sharing needles or through unprotected sex, although some infections can be traced to a transfusion of contaminated blood.

Symptoms may include fever, fatigue and nausea, but many people who develop an acute hepatitis C infection do not realize it.

However, in up to 84% of cases the acute infection will eventually lead to chronic hepatitis C.

The researchers gave daily injections of interferon to volunteers for the first four weeks of therapy.

They received the drug three times a week for the remainder of the study.

The doctors found that, on average, the virus had dropped to undetectable levels after about 3.2 weeks of treatment.

After two years, only one of the 44 patients had any trace of the virus in their blood.

In a similar group of 40 untreated patients, chronic hepatitis C developed in 28.

The interferon was supplied by Essex-Pharma of Munich, which paid for the study. Two of the 10 authors have financial ties to the company.

The research will appear in the New England Journal of Medicine.