Hepatitis is a general term that means inflammation of the liver. It can be acute or chronic and has a number of different causes. It can be caused by a group of viruses known as the hepatitis viruses, including A, B, C, D and E. Other viruses may also be the culprit, such as those that cause mononucleosis (the Epstein-Barr virus) or chickenpox (the varicella virus).
Hepatitis also applies to inflammation of the liver caused by drugs and alcohol abuse or toxins in the environment. In addition, people also can develop hepatitis from other factors, such as fat accumulation in the liver (called fatty liver disease), trauma or an autoimmune process in which a person's body makes antibodies that attack the liver.
Viral hepatitis is common. Thousands of cases are reported to the CDC each year, but researchers estimate that the true number of people in the United States who have the disease (acute and chronic) is much higher than the number reported.
Many hepatitis cases go undiagnosed because they are mistaken for the flu. Hepatitis can be serious because it interferes with the liver's many functions. Among other things, the liver produces bile to aid digestion, regulates the chemical composition of the blood, and screens potentially harmful substances from the bloodstream.
The five hepatitis viruses can be transmitted in different ways, but they all have one thing in common: They infect the liver and cause it to become inflamed. Generally, the acute phase of the disease lasts from two to three weeks; complete recovery takes about nine weeks. Many patients recover with a lifelong immunity to the disease, but a few hepatitis victims (less than 1%) die in the acute phase. Hepatitis B and C may progress to chronic hepatitis, in which the liver remains inflamed for more than six months. This condition can lead to cirrhosis and possibly death.
Although their effects on the liver and the symptoms they produce can be similar, the various forms of hepatitis are contracted in different ways. In the case of viral hepatitis, the severity and duration of the disease are largely determined by the organism that caused it.
Hepatitis A, which is generally contracted orally through fecal contamination of food or water, is considered the least dangerous form of the disease because it almost always resolves on its own. Also, it does not lead to chronic inflammation of the liver. The hepatitis A virus commonly spreads through improper handling of food, contact with household members, sharing toys at day-care centers, and eating raw shellfish taken from polluted waters.
Hepatitis B can spread through sexual contact, blood transfusions, and needle sharing by intravenous drug users. The virus can pass from mother to child at birth or soon afterward; the virus can also travel between adults and children to infect whole families. In over half of all hepatitis B cases the source cannot be identified.
The majority of adults with hepatitis B recover completely, but a small percentage of them can't shake the disease and become carriers. Carriers can transmit the disease to others even when their own symptoms have vanished. A smaller percentage of patients who cannot fight off the virus will develop chronic hepatitis B. Like carriers, those with chronic hepatitis B are able to pass on the virus. Up to 25% of chronic hepatitis B patients die prematurely from the disease as a result of cirrhosis or liver cancer.
Hepatitis C is usually spread through contact with blood or contaminated needles -- including tattoo needles. Although hepatitis C may cause only mild symptoms or none at all, approximately 20% of those infected develop cirrhosis within 20 years. The disease can be passed on through blood transfusions, but screening, which started in the early '90s, has greatly reduced the number of such cases. In a third of all hepatitis C cases, the source of the disease is unknown.
Hepatitis D occurs only in people infected with hepatitis B and tends to magnify the severity of that disease. It can be transmitted from mother to child and through sexual contact. Although less common, hepatitis D is especially dangerous because it involves two distinct viruses working at once.
Hepatitis E occurs mainly in Asia, Mexico, India, and Africa; only a few cases are reported in the United States, mostly among people who have returned from a country where the disease is widespread. Like hepatitis A, this type is usually spread through fecal contamination, and it does not lead to chronic hepatitis. This form is considered slightly more dangerous than hepatitis A. It can cause severe disease and death in pregnant women.
Other viruses. Other viruses may also be responsible for causing hepatitis. These include the Epstein-Barr virus (often associated with mononucleosis), the varicella virus (which causes chickenpox), the herpes simplex virus (HSV), and cytomegalovirus (CMV).
Alcoholic, toxic, and drug-related hepatitis can produce the same symptoms and liver inflammation that result from viral hepatitis. This form is caused not by invading microorganisms but by excessive and chronic consumption of alcohol, ingestion of environmental toxins, or misuse of certain prescription drugs and over-the-counter medications such as acetaminophen.