What is the infectious agent that causes hepatitis B virus infection?
Hepatitis B infection is caused by the hepatitis B virus. Hepatitis B virus is present in the blood and body fluids of infected persons.

Where is hepatitis B virus infection found?
Hepatitis B infection occurs worldwide.

How do people get hepatitis B infection?
Hepatitis B virus is easily spread by direct contact with the blood or body fluids of an infected person. For example, hepatitis B can be transmitted from an infected mother to her baby at birth, through unprotected sex with an infected person, by sharing equipment for injecting street drugs, and by occupational contact with blood in a health-care setting. Hepatitis B is not spread through food or water or by casual contact.

People can have hepatitis B (and spread the disease) without knowing it. Sometimes, people who are infected with hepatitis B virus never recover fully from the infection. They carry the virus and can infect others for the rest of their lives.

What are the signs and symptoms of hepatitis B?
Many persons who are infected with hepatitis B virus have no symptoms. Others become ill with these symptoms:

• Loss of appetite
• Tiredness
• Pain in muscles, joints, or stomach
• Diarrhea or vomiting
• Jaundice (yellowing of the skin and whites of the eyes)

What complications can result from hepatitis B?
Most infected persons clear the hepatitis B virus out of their systems completely in a few months. In some people, especially infants and children, hepatitis B virus can cause chronic (lifelong) liver infection. Chronic infection can lead to liver damage (cirrhosis), liver cancer, and death.

How is hepatitis B diagnosed?
Hepatitis B can be diagnosed by a blood test.

Who is at risk for hepatitis B?
Anyone can get hepatitis B, but the risk is higher if a person:

• Has sex with someone infected with hepatitis B virus
• Has sex with more than one partner
• Is a man who has sex with another man
• Lives in the same house with someone who has lifelong hepatitis B virus infection
• Has a job that involves contact with human blood
• Injects illegal drugs
• Is a patient or worker in a home for the developmentally disabled
• Has hemophilia
• Moves or travels often to areas where hepatitis B is common

Persons whose parents were born in some parts of China, Southeast Asia, Africa, the Amazon Basin in South America, the Pacific islands, and the Middle East are also at high risk.

What is the treatment for hepatitis B?
There is no cure for hepatitis B. Treatment includes rest and proper diet.

How common is hepatitis B infection?
Hepatitis B is a very common infection. Each year in the United States, an estimated 200,000 persons are newly infected with hepatitis B virus. More than 11,000 of these people are hospitalized, and 20,000 remain chronically infected. Overall, an estimated 1.25 million people in the United States have chronic hepatitis B virus infection, and 4,000 to 5,000 people die each year from liver disease or liver cancer related to hepatitis B. Nearly 300 million persons in the world are chronically infected with hepatitis B virus. High rates of chronic infection are found in some parts of China, Southeast Asia, Africa, the Pacific islands, the Amazon Basin in South America, and the Middle East.

How can hepatitis B be prevented?
Hepatitis B vaccine is the best protection against hepatitis B virus. The vaccine prevents both hepatitis B virus infection and the chronic diseases related to hepatitis B. Three shots are needed for complete protection. Hepatitis B vaccine is recommended for:

• All newborn babies
• All children 11-12 years of age who have not been vaccinated
• Persons of any age whose behavior or job puts them at high risk for hepatitis B virus infection

All pregnant women should be tested for hepatitis B virus early in their pregnancy. If the blood test is positive, the baby should receive hepatitis B vaccine at birth, along with another shot (hepatitis B immune globulin). If the blood test shows that the mother is not infected, vaccination of the baby can be delayed until age 2-6 months. This delay responds to concerns that the small amounts of mercury in the vaccine preservative thimerosal could pose a theoretical risk to newborn infants, although no scientific evidence of harm caused by this level of exposure has been reported. When a new hepatitis B vaccine that does not contain the preservative thimerosal becomes available, newborn hepatitis B vaccination does not need to be delayed and can start at birth.

Hepatitis B vaccine has been available since 1982 and has been shown to be very safe when given to infants, children, and adults. More than 200 million doses of hepatitis B vaccine have been administered in the United States, including more than 50 million doses administered to infants and young children. The most common side effect from hepatitis B vaccination is temporary pain at the injection site, occurring in about 3%-9% of children and adolescents and 13%-29% of adults. The second most commonly reported side effect is mild to moderate fever, occurring in about 4%-7% of children and 1% of adults. Studies show that these side effects are reported no more often among vaccinated persons than among persons not receiving vaccine.