Q: What is hepatitis C and how do you get it?
A: In the mid-1970s doctors recognized that most cases of hepatitis following blood transfusion were not due to either of the two then-known hepatitis viruses, hepatitis A and B. For a while, this complication of transfusions was designated non-A non-B hepatitis. A long search for the cause of this form of hepatitis culminated in 1988 with the identification of the hepatitis C virus and the subsequent development of laboratory tests to detect infections with the virus.
Hepatitis C has caused about 80 percent of post-transfusion hepatitis, but the introduction in May 1990 of laboratory tests to screen donated blood for this virus has greatly reduced the risk to blood recipients.
IV drug abuse is the source of one-third of the infections in this country: Studies have shown that 50 to 80 percent of IV drug abusers test positive for hepatitis C. The virus also can be transmitted by accidental needle pricks among medical personnel. The source of hepatitis C cannot be identified in nearly half the cases. Possibilities include sexual transmission, contact with blood on a razor or toothbrush, and even insect bites (since the hepatitis C virus belongs to the same family of viruses that are transmitted by insects).
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine and associate dean for faculty affairs at the school.