Hepatitis B

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.

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.

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:

  • fatigue
  • nausea
  • dark urine
  • muscle soreness
  • vomiting
  • loss of appetite
  • stomach pain
  • jaundice

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.

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?

When infected, the liver becomes inflamed, which may cause the healthy, soft tissues in the liver to harden and scar. If not stopped, inflammation and scarring can lead to serious liver diseases such as cirrhosis or liver cancer. If the damage is severe enough, the liver may not perform all of its functions normally.

How we care for hepatitis B

The Center for Childhood Liver Disease at Boston Children's Hospital is one of the leading centers in the world for the care of children with chronic hepatitis B. The center’s director, Maureen Jonas, MD, is a national leader in the care, diagnosis, and treatment for children with hepatitis. Dr. Jonas, along with her team, wrote the clinical guidelines that shape the way pediatric GI specialists and pediatricians around the country treat chronic hepatitis B.

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.