CausesBy Mayo Clinic staff
Hepatitis B infection is caused by the hepatitis B virus (HBV). The virus is passed from person to person through blood, semen or other body fluids. When HBV enters your liver, it invades the liver cells and begins to multiply. This causes inflammation in the liver and leads to the signs and symptoms of hepatitis B infection.
Common ways HBV is transmitted include:
- Sexual contact. You may become infected if you have unprotected sexual contact with an infected partner whose blood, saliva, semen or vaginal secretions enter your body.
- Sharing of needles. HBV is easily transmitted through needles and syringes contaminated with infected blood. Sharing intravenous (IV) drug paraphernalia puts you at high risk of hepatitis B.
- Accidental needle sticks. Hepatitis B is a concern for health care workers and anyone else who comes in contact with human blood.
- Mother to child. Pregnant women infected with HBV can pass the virus to their babies during childbirth.
Acute vs. chronic hepatitis B
Hepatitis B infection may be either short-lived (acute hepatitis B) or long lasting (chronic hepatitis B).
- Acute hepatitis B infection lasts less than six months. If the disease is acute, your immune system is usually able to clear the virus from your body, and you should recover completely within a few months. Most people who acquire hepatitis B as adults have an acute infection.
- Chronic hepatitis B infection lasts six months or longer. When your immune system can't fight off the virus, hepatitis B infection may become lifelong, possibly leading to serious illnesses such as cirrhosis and liver cancer. Most infants infected with HBV at birth and many children infected between 1 and 5 years of age become chronically infected. Chronic infection may go undetected for decades until a person becomes seriously ill from liver disease.
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