Hepatitis B (HBV, Hep B)

  • Medical Author:
    Mary D. Nettleman, MD, MS, MACP

    Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

  • Medical Author: Mohamad El Mortada, MD
  • Medical Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Quick GuideHepatitis C, Hepatitis B, and Hepatitis A: Symptoms, Causes, Treatment

Hepatitis C, Hepatitis B, and Hepatitis A: Symptoms, Causes, Treatment

What is hepatitis?

The term 'hepatitis' simply means inflammation of the liver. Hepatitis may be caused by a variety of viruses or other infections, medications, or a toxin such as alcohol. Hepatitis viruses that can cause injury to liver cells in addition to hepatitis B include the hepatitis A and hepatitis C viruses. These viruses are not related to each other or to the hepatitis B virus, and they differ in their structure, the ways they are spread among individuals, the severity of symptoms they can cause, the way they are treated, and the outcome of the infection. Other hepatitis viruses (hepatitis D, hepatitis E, and hepatitis G) cause disease much less commonly.

Other viruses that infect the liver but which are not specifically "hepatitis viruses" include Epstein-Barr virus (EBV, the virus that causes mononucleosis) and cytomegalovirus (CMV).

What is the scope of the problem?

Hepatitis B is an infection of the liver caused by the hepatitis B virus (HBV). It is estimated that 2 billion people  worldwide have evidence of current or past hepatitis B infection, including more than 250 million chronic carriers and more than 600,000 deaths worldwide each year. According to the Centers for Disease Control (CDC), approximately 19,000 new cases of hepatitis B occurred in the United States in 2013.

In the United States, rates of new infection were highest among people aged 25 to 44 years (3.1 cases per 100,000 population) and lowest among those younger than 15 years of age (0.02 per 100,000). This reflects the major modes of transmission of hepatitis B (sexual transmission, illicit drug use, exposure to infected blood) and the effect of universal vaccination of infants. In the United States, there has been a 82% decrease in newly diagnosed cases of hepatitis B since 1990. This decrease is attributed to increased vaccination and to heightened public awareness of HIV/AIDS and the resulting safer sexual practices.

When a person first gets hepatitis B, they are said to have an 'acute' infection. Most people are able to eliminate the virus and are cured of the infection. Some are not able to clear the virus and have 'chronic' infection with hepatitis B that is usually life-long (see below). In the United States an estimated 2.2 million people are chronically infected with hepatitis B.

Hepatitis B is found throughout the world. Some countries have much higher rates of infection than the United States; for example, in Southeast Asia and Sub-Saharan Africa, as many as 15% to 20% of adults are chronically infected with hepatitis B.

What kind of a virus is hepatitis B?

The hepatitis B virus is a DNA virus, meaning that its genetic material is made up of deoxyribonucleic acids. It belongs to a family of viruses known as Hepadnaviridae. The virus is primarily found in the liver but is also present in the blood and certain body fluids.

Hepatitis B virus consists of a core particle (central portion) and a surrounding envelope (outer coat). The core is made up of DNA and the core antigen (HBcAg). The envelope contains the surface antigen (HBsAg). These antigens are present in the blood and are markers that are used in the diagnosis and evaluation of patients with suspected viral hepatitis.

How does hepatitis B virus cause liver injury?

The hepatitis B virus reproduces in liver cells, but the virus itself is not the direct cause of damage to the liver. Rather, the presence of the virus triggers an immune response from the body as the body tries to eliminate the virus and recover from the infection. This immune response causes inflammation and may seriously injure liver calls. Therefore, there is a balance between the protective and destructive effects of the immune response to the hepatitis B virus.

Medically Reviewed by a Doctor on 2/29/2016

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