How contagious is hepatitis C? Does it make a difference if someone is newly or chronically infected?

S.W.

The hepatitis C virus (HCV) is a cause of hepatitis that is most commonly acquired through blood contact. Before tests became available for HCV, it was often transmitted through blood transfusions. Today, it is most commonly seen among intravenous drug users who share needles, patients on chronic hemodialysis, and healthcare workers who have been stuck with needles. Besides blood-borne transmission, HCV can be spread through sexual contact and from mother to infant. There are also a substantial proportion of cases in which no obvious risk factor for infection is present. So, there may be other modes of HCV transmission that have not yet been discovered.

The efficiency of HCV transmission, or how "contagious" it is, relates to the way in which it is transmitted. The blood-borne route (via needles or transfusions) appears to be most efficient. Studies have found that up to 10 percent of healthcare workers stuck by HCV-contaminated needles become infected with HCV. Sexual and mother-to-infant transmission rates are much lower.

To answer your second question, doctors currently do not know whether the stage of infection (new or chronic) makes a difference in how infectious a person with HCV is. However, it is known that if the person is also infected with the AIDS-causing human immunodeficiency virus (HIV), transmission of HCV is more likely.

Regardless of the mode of transmission, the strategy for treating HCV remains the same. Since more than 80 percent of HCV-infected patients develop chronic hepatitis, most people infected with HCV are potential candidates for therapy. Evaluation includes blood tests to assess the amount of active virus in the blood, and a liver biopsy may be done to evaluate the amount of inflammation and scarring. The process by which HCV causes liver inflammation and scarring usually takes at least a decade, but these potentially life-threatening complications may occur in up to 20 percent of infected patients.

Therapy to prevent the complications of HCV includes a combination of oral ribavirin and injections of interferon. This drug combination, given for six to 12 months, leads to long-term remission rates of up to 40-45 percent. You can get additional information on HCV therapy from your doctor.