Hepatitis C - Only discovered in 1988, it is a leading cause of cirrhosis and liver cancer and is the main cause of liver transplants in the United States. It is not as infectious as hepatitis A or B but is spread through blood and shared needles. There is no cure or vaccine but drugs such as interferon alfa and ribavirin seem to help. A report in January in the New England Journal of Medicine warned that people with hepatitis C faced a dramatically higher risk of dying if they eat food infected with hepatitis A. Hepatitis D - Associated with hepatitis B infection. People with both hepatitis B and D have an 80 percent chance of chronic liver disease.
Drug users are the group at highest risk.
Only three known strains have been identified globally. It is a major cause of liver failure in developing nations. Passed in the feces, and blood, infection is devastating to pregnant women, killing 10 to 20 percent of women infected in their third trimester. Hepatitis G - Very rare, it causes up to 2,000 infections a year but most victims have no symptoms. It is transmitted in infected blood and repeated exposure to hepatitis C seems to be a risk factor.