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What is hepatitis B?

Hepatitis B is a liver disease caused by the hepatitis B virus (HBV). Since 1991 when children started getting routinely vaccinated for the virus, cases of hepatitis B in the U.S. have gone down 82 percent, according to the Centers for Disease Control and Prevention.

HBV spreads through blood, saliva, or other bodily fluids. The most common way children become infected with hepatitis B is if they are born to a mother with the virus. Older children can become infected through injection drug use or unprotected sex.

There are two phases of hepatitis B: acute and chronic.

  • Acute hepatitis B is often a mild or asymptomatic illness that may clear on its own in a matter of weeks. The younger the patient, the less likely the virus will be cleared on its own, and the more likely the infection will become chronic. Children and adults who are not able to clear an HBV infection within six months are considered to have chronic hepatitis B.
  • Chronic hepatitis B may be a serious illness that can cause long-term health problems. Over time, the liver may remain healthy or may develop progressive scarring, leading to cirrhosis. Chronic hepatitis B is the most common cause of liver cancer in the world.

Over the course of decades, chronic hepatitis B progresses through four stages — immune tolerance, immune clearance, inactive (latent), and reactivated — based on the behavior of the virus and how the child’s immune system responds against it. The inactive carrier phase can last for years, often well into adulthood.

What is the liver, and what does it do?

The liver is the second largest organ in the body, located in the abdominal cavity. The liver helps the body in many ways:

  • the liver produces proteins that allow blood to clot normally, transport oxygen, and support the immune system
  • it produces bile, a substance that helps digest food
  • it stores extra nutrients
  • it helps clean the bloodstream of harmful substances
  • it helps control blood sugar and cholesterol levels

How does hepatitis B affect the liver?

In acute symptomatic hepatitis B, the liver can become swollen and inflamed. However the infection is often silent, particularly in infants. If the infection becomes chronic, the virus can cause inflammation and cause the healthy, soft tissues of the liver to harden and scar. About a quarter of people with chronic hepatitis B develop serious liver diseases such as cirrhosis or liver cancer.

Hepatitis B | Symptoms & Causes

What are the symptoms of hepatitis B?

The majority of children with acute hepatitis B have no symptoms. Parents typically have no idea their child is infected. Over time, as the virus causes increasing damage to the liver, the following symptoms may appear:

What causes hepatitis B?

Hepatitis B is caused by the hepatitis B virus (HBV). The virus is passed from person to person through contact with blood infected with HBV, sexual intercourse, or intravenous drug use. Mothers infected with HBV can pass the virus on to their children during childbirth, though doctors can reduce that risk by giving newborns both the hepatitis B vaccine and a medication called hepatitis B immune globulin (or HBIG) within about 12 hours of birth.

While the number of new cases of hepatitis B in the United States has dropped dramatically in the last two decades — thanks to the vaccination — the Centers for Disease Control and Prevention estimates between 885,000 and 2.2 million people in the U.S. have chronic HBV infection.

Hepatitis B | Diagnosis & Treatments

How is hepatitis B diagnosed?

A doctor who suspects that a child is infected with HBV may test the child’s blood to see if it contains a portion of the virus called the surface antigen. If the test comes back positive, the doctor may run additional tests for the other portions of the virus that can provide more information.

Children and adults with HBV surface antigen in their blood for more than six months typically undergo periodic tests to monitor their liver function and look for signs of serious liver disease. If such tests show that the virus is starting to damage the child’s liver, doctors may order a biopsy to determine if it is appropriate to start treatment.

The doctor will likely ask about family history of liver disease, in particular liver cancer. Knowing the family’s health history can help predict how the virus will affect the child.

How is hepatitis B treated?

Doctors treat acute and chronic hepatitis B very differently. In prescribing treatment for hepatitis B, doctors aim to disable the virus, reduce the amount of virus in the blood, and prevent liver damage that could lead to cirrhosis or liver cancer.

If a child has acute hepatitis B, doctors will recommend rest, healthy eating, and drinking plenty of fluids. If the infection has lasted more than six months and doctors see signs of liver damage, they may recommend starting treatment with one of a variety of medications.

Should a child with hepatitis B get the hepatitis vaccine?

While the hepatitis B vaccine is not effective in anyone already infected with the virus, any child or adult with hepatitis B should receive the vaccine against hepatitis A in order to prevent additional liver inflammation and injury. There is currently no vaccine for hepatitis C.

What is the long-term impact of chronic hepatitis B?

Children with chronic hepatitis B can lead completely normal lives, attend school, and play sports without any special arrangements, just like any other child.

A child with chronic HBV infection could be infected for life. Over the decades, the virus can cause progressive damage to the liver and lead to such complications as cirrhosis and liver cancer.

When they become older, children with hepatitis B should avoid drinking alcohol, as it can make the disease progress more quickly. Once they become sexually active, they should practice safe sex to protect their partners from infection.

Hepatitis B | Research & Innovation

Our areas of innovation for hepatitis B

Liver biopsies provide a great deal of information about the extent of damage in a child’s liver, but the procedure is invasive and can be both painful and risky. Researchers at Boston Children’s are investigating an ultrasound-based imaging technology called FibroScan™ that may be able to help doctors assess liver scarring without the need for a biopsy.

Hepatitis B | Programs & Services