Hepatitis is inflammation of the liver. The liver has many functions, among them the secretion of bile, a solution critical to fat emulsion and absorption. The liver also removes excess glucose from circulation and stores it until it is needed. It converts excess amino acids into useful forms and filters drugs and poisons from the bloodstream, neutralizing them and excreting them in bile. Hepatitis affects the liver?s ability to perform these life-preserving functions.

Hepatitis A virus (HAV) lives in feces in the intestinal tract. It is spread when infected individuals do not wash their hands after using the toilet and then handle food, or when a person changes an infected infant?s diapers and then handles food before washing his or her hands. People who eat this contaminated food run a high risk of becoming infected. The virus also spreads when drinking water is contaminated with raw sewage. When people use contaminated water for drinking, as ice, or to wash fruits or vegetables, they run the risk of contracting HAV. Eating raw or partially cooked shellfish harvested from water contaminated with raw sewage can also lead to HAV infection.

Experts estimate that roughly 125,000 to 200,000 cases of hepatitis A infections occur in the United States each year. Individuals with hepatitis A can spread the disease to others as early as two weeks before symptoms appear. In addition to the general hepatitis symptoms, such as nausea, fatigue, and jaundice, hepatitis A may also cause diarrhea. There is no treatment for hepatitis A. Most people will recover on their own without any serious aftereffects, although a few severe cases may require a liver transplant.

The hepatitis B virus (HBV) lives in blood and other body fluids. HBV is transmitted from person to person through unprotected sexual intercourse with an infected person, or through the sharing of infected needles or other sharp instruments that break the skin. Babies born to an infected mother have a 90 to 95 percent chance of contracting HBV during childbirth. If a baby is infected, the virus remains in its body for many years, silently attacking liver cells and eventually leading to cirrhosis or, in some cases, cancer of the liver. Even though an infected baby may show few or no signs of infection, the infant continues to be infectious and can pass the virus on to others. In up to 10 percent of HBV infections, patients develop chronic hepatitis B.

Experts estimate that there are 140,000 to 320,000 hepatitis B infections every year in the United States. Although researchers are investigating promising new treatments for hepatitis B, the only one currently available is interferon, a drug that is effective in only 35 to 40 percent of patients treated. Liver transplants may be beneficial to infected patients, but the virus remains in the body after transplantation surgery and may eventually attack the new liver.

The hepatitis C virus (HCV), identified in the mid-1980s, is a slowly progressing infection that is primarily spread by intravenous drug users. According to the Centers for Disease Control and Prevention (CDC), anyone who received a blood transfusion prior to 1992, before an accurate routine blood screening was established, may be infected with this virus. HCV can also be spread through the sharing of toothbrushes, razors, and contaminated needles with an infected person; through unprotected sex with an infected person; and from mother to child during childbirth.

An estimated 36,000 cases of hepatitis C develop each year, and although some resolve spontaneously, 80 to 85 percent of all cases progress to chronic hepatitis. Most of the 3.9 million people with chronic hepatitis C in the United States do not look sick and may not even know they are infected. Interferon is also used to treat HCV, but it is effective in only 20 to 30 percent of cases. In 1998, a new combination of drugs was approved to treat some cases of hepatitis C. The therapy, a combination of interferon and the antiviral drug ribavirin, has been approved to treat hepatitis in those people who relapse after treatment with interferon.

Hepatitis D virus (HDV), found in blood, is transmitted through the sharing of infected needles or through sexual contact with an infected person. But HDV is a parasite of HBV, using the B virus to reproduce itself and survive in the body. Only those infected with HBV are susceptible to HDV infection. Hepatitis E virus (HEV) lives in feces and is transmitted through contaminated food or water. Hepatitis E is found primarily in countries with poor sanitation. A hepatitis G virus has also been identified and is under scientific investigation, and researchers believe there may be still other hepatitis viruses as yet unknown.
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