Hepatitis - Introduction

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Acute Hepatitis. Acute hepatitis can begin suddenly or gradually, but it has a limited course and rarely lasts beyond 1 or 2 months, although it may last up to 6 months. Usually, there is only minimal liver cell damage and evidence of immune system activity. Rarely, acute hepatitis due to hepatitis B can cause severe, even life-threatening, liver damage.

Chronic Hepatitis. If hepatitis does not resolve after 6 months, it is considered chronic. The chronic forms of hepatitis last for prolonged periods. Doctors usually categorize chronic hepatitis by indications of severity:

• Chronic persistent hepatitis is usually mild and does not progress or progresses slowly, causing limited damage to the liver.
• Chronic active hepatitis involves progressive and often extensive liver damage and cell injury.

Click the icon to see an image of aggressive hepatitis.

Viral Hepatitis

Most cases of hepatitis are caused by viruses that infect liver cells and begin multiplying. They are identified by the letters A through G:

• Hepatitis A, B, and C are the most common viral forms of hepatitis and are the primary focus of this report.
• Other hepatitis viruses include hepatitis D and E. Hepatitis D is a serious but uncommon form of hepatitis that can be chronic. It is associated with hepatitis B, as the D virus relies on the B virus to replicate. (Therefore, hepatitis D cannot exist without the B virus also being present.) Hepatitis E, like hepatitis A, is an acute form of hepatitis that is transmitted by contact with contaminated food or water.
• Researchers are investigating additional viruses that may be implicated in hepatitis unexplained by the currently known viruses.

The name of each type of viral hepatitis condition corresponds to the virus that causes it. For example, hepatitis A is caused by hepatitis A virus (HAV), hepatitis B is caused by hepatitis B virus (HBV), and hepatitis C is caused by hepatitis C virus (HCV).

Scientists do not know exactly how these viruses actually cause hepatitis (inflammation in the liver). As the virus reproduces in the liver, several proteins and enzymes, including many that attach to the surface of the viral protein, are also produced. Some of these may be directly responsible for liver damage.