HEPATITIS

inflammation of the liver that results from a variety of causes, both infectious and noninfectious. Infectious agents that cause hepatitis include viruses and parasites; noninfectious substances include certain drugs and toxic agents. In some instances hepatitis results from an autoimmune reaction directed against the liver cells of the body. Most cases of hepatitis are caused by viral infection. The viruses that give rise to liver inflammation include cytomegalovirus, yellow fever virus, Epstein-Barr virus, and a number of hepatitis viruses. The term viral hepatitis, however, usually is applied only to those cases of liver disease caused by the hepatitis viruses. There are seven known hepatitis viruses, which are labeled A, B, C, D, E, F, and G. Hepatitis A, E, and F viruses are transmitted through the ingestion of contaminated food or water (called the fecal-oral route), and the spread of these agents is aggravated by crowded conditions and poor sanitation. The B, C, D, and G viruses are transmitted mainly by blood or bodily fluids, and thus sexual contact or exposure to contaminated blood are common modes of transmission. The signs and symptoms of acute viral hepatitis are similar, regardless of the hepatitis virus responsible. Patients may experience a flulike illness, and general symptoms include nausea, vomiting, abdominal pain, fever, fatigue, loss of appetite, and, less commonly, rash and joint pain. Sometimes a condition called jaundice-a yellowing of the skin and eyes-will develop. These symptoms result from the damage the virus inflicts on the liver cells. The acute symptomatic phase of viral hepatitis usually lasts from a few days to several weeks; the period of jaundice that may follow can persist from one to three weeks. Complications of acute viral hepatitis include fulminant hepatitis, which is a very severe, rapidly developing form of the disease, and chronic hepatitis, which is characterized by liver cell death and inflammation that last longer than six months. Hepatitis A, caused by the hepatitis A virus (HAV), is the most common worldwide. The onset of hepatitis A usually occurs in 15 to 45 days after exposure to the virus, and some infected individuals, especially children, exhibit no clinical manifestations. Most recover fully from the disease. In the majority of cases, no special treatment other than bed rest is required. Hepatitis A does not give rise to chronic hepatitis. The severity of the disease can be reduced if within two weeks of exposure the individual is injected with immune serum globulin obtained from persons exposed to HAV. This approach, called passive immunization, is effective because the serum contains antibodies against HAV. Vaccines against HAV have also been developed, although they are expensive and the duration of protection is not known. Hepatitis B is a much more severe and longer-lasting disease than hepatitis A. It may occur as an acute disease of short duration or, in about 5 to 10 percent of cases, the illness may become chronic and lead to permanent liver damage. Symptoms of hepatitis B usually appear from 40 days to 6 months after exposure. Those persons at greatest risk for contracting hepatitis B include intravenous drug users, sexual partners of individuals with the disease, health care workers, and recipients of organ transplants or blood transfusions. A safe and effective vaccine against HBV is available, providing protection for at least five years. Passive immunization with hepatitis B immune globulin can also provide protection. Those who carry the virus are 100 times more likely to develop liver cancer than persons without HBV in their blood. Hepatitis C virus (HCV), previously referred to as non-A, non-B hepatitis, was isolated in 1988. Symptoms of hepatitis C usually appear within six to nine weeks after exposure. Transmission of HCV occurs in a fashion similar to HBV transmission, although it seems that HCV infection occurs less readily via sexual contact than does HBV. Hepatitis C has a greater propensity than hepatitis B to develop into chronic liver disease. The only approved treatment for hepatitis C in the United States is alpha interferon, and only about half of those receiving the drug respond to it. Infection with hepatitis D virus (HDV), also called the delta agent, can occur only in association with HBV infection, because HDV requires HBV to replicate. Infection with HDV may occur at the same time infection with HBV occurs, or HDV may infect a person already infected with HBV. The latter situation appears to give rise to a more serious condition, leading to cirrhosis or chronic liver disease. Alpha interferon is the only treatment for HDV infection. Preventing infection with HBV also prevents HDV infection. Discovered in the 1980s, the hepatitis E virus (HEV) is similar to HAV. HEV is transmitted in the same manner as HAV, and it, too, only causes acute infection. However, the effects of infection with HEV are more severe than those caused by HAV, and death is more common. The risk from infection with HEV is especially great for pregnant women. HEV is responsible for widespread epidemics of hepatitis in less-developed countries, including Mexico, India, and Africa, that occur as a result of ingestion of contaminated water or food (enteric transmission). Prior to the discovery of HEV, hepatitis E was called enterically transmitted non-A, non-B hepatitis. Some cases of hepatitis transmitted through contaminated food or water are not caused by HAV or HEV but instead are attributed to the hepatitis F virus (HFV), which was first reported in 1994. Another virus isolated in 1996, the hepatitis G virus (HGV), is believed to be responsible for a large number of sexually transmitted and bloodborne cases of hepatitis. HGV causes both acute and chronic forms of the disease and often infects persons already infected with HCV. Most cases of chronic hepatitis are caused by the hepatitis viruses HBV, HCV, and HDV, but other factors such as alcoholism, reaction to certain medications, and autoimmune reactions lead to the development of the disease. Chronic hepatitis may also be associated with some illnesses, such as Wilson's disease, and alpha-1-antitrypsin deficiency. Chronic hepatitis B primarily affects males, whereas chronic hepatitis C arises in equal numbers in both genders. Autoimmune hepatitis generally occurs in young women. Treatment for autoimmune hepatitis includes corticosteroids, which help to reduce symptoms. Alcoholic hepatitis results from sustained consumption of excessive amounts of alcohol. The condition can be reversed if it is caught early enough and the individual either significantly reduces or entirely curtails intake of alcohol. If untreated it can give rise to alcoholic cirrhosis.