Whether insect bites can transmit this virus isn't clear. Many cases of hepatitis B have no known source. In areas of the world such as the Far East and parts of Africa, hepatitis B virus is responsible for many cases of chronic hepatitis, cirrhosis, and liver cancer. Hepatitis C virus causes at least 80 percent of the hepatitis cases arising from blood transfusions, plus many scattered cases of acute hepatitis. It is most commonly transmitted by injecting drug users who share needles.
Sexual transmission is uncommon.
Hepatitis C virus is responsible for many cases of chronic hepatitis and some cases of cirrhosis and liver cancer. A small proportion of healthy people appear to be chronic carriers of the hepatitis C virus. Hepatitis D virus occurs only as a co-infection with hepatitis B virus, and it makes the hepatitis B infection more severe. Drug addicts are at relatively high risk. Hepatitis E virus causes occasional epidemics similar to those caused by hepatitis A virus.