Perhaps the first account of hepatitis occurred in the second century b.c., when Greek physicians described a mysterious and often fatal disease that caused inflammation of the liver. They noted that the skin of afflicted patients had a distinguishing yellow appearance, later called jaundice. A thousand years later, St. Zacharias (d.752) described a similar disease; and, between the seventeenth and nineteenth centuries, about 80 epidemics of jaundice occurred throughout the world. Today, it is known that hepatitis can cause a variety of other symptoms, including malaise, liver disease, gastrointestinal upset, liver cancer, and scarring of the liver (cirrhosis). When the liver becomes infected and inflamed, it is unable to perform its vital functions. This causes a reduction in the blood flow to the liver and subsequent cell death. Cirrhosis may follow.
Many types of hepatitis can be prevented, however. Alcoholic hepatitis is caused by an increase in the fat deposits within the liver. This non-infectioustype of hepatitis is common among heavy drinkers. There are also several types of hepatitis caused by viruses. These include hepatitis types A, B, C, andD.
Hepatitis A, also known as epidemic or infectious hepatitis, is spreadby the intestinal-oral route. Infection occurs in conditions of poor sanitation and overcrowding. Once the virus has been contracted, it usually takes about 20-40 days before symptoms appear. This is known as the incubationperiod.
Hepatitis B, or serum hepatitis, is transmitted mainly by blood transfusion.Sexual transmission of hepatitis B has also been reported. The incubation period takes between 60 and 180 days. Type B viral hepatitis (HBV) has a higherfatality rate than type A.
Hepatitis C, also referred to as non-A, non-B hepatitis (NANB), is also transmitted through blood transfusion. Researchers believe that the causative agent may actually be several viruses. A 1998 study from Scotland has found thathepatitis C might also be spread through saliva, which may account for the fifty percent of cases in which there is no history of blood transfusions or intravenous drug use. People infected with epatitis C usually show relatively mild symptoms which may become chronic.
In 1977, hepatitis D was discovered and found to be present only in the livercells of people who had been exposed to HBV. Scientists strongly believe that this virus requires HBV to survive. Hepatitis D is an important factor in the development of chronic liver disease.
Many other viruses can cause hepatitis, including Epstein-Barr, herpes simplex, measles, mumps, and chicken pox viruses.
Many methods are available to help prevent transmission of viral hepatitis. Maintaining clean living conditions, designing adequate sewage facilities, andtesting blood supplies for contamination are obvious approaches. Baruch S. Blumberg (1925-) and Irving Millman (1923-) developed a test to identify hepatitis B in blood samples, which helped blood banks screen out carriersof hepatitis B after they began using the test in 1971. The test was based onBlumberg's discovery of an antigen that detected hepatitis B in blood samples.
One of the best modes of prevention is vaccination. Safe and effectivevaccines are now available for protection against hepatitis B, including onedeveloped by Blumberg and Millman. In 1986, a new type of vaccine that usedgenetic engineering was developed. Scientists were able to make the vaccine by inserting part of the HBV gene into baker's yeast cells. The yeast cells then produced large amounts of viral protein. This protein resembled the infectious hepatitis virus but lacked certain parts that would cause the disease inhumans. The viral protein was then injected into the human body, causing theimmune system to produce antibodies against the virus, thus creating an immunity against hepatitis B. This yeast-derived hepatitis B vaccine is the firstrecombinantly produced vaccine approved for human use.
Studies continue into the treatment of hepatitis. Injections of interferon alfa has been approved for treatment of hepatitis B and C; and a number of newdrugs, called nucleoside analogues, are also be developed for treating hepatitis B.