Causes

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. It does not spread by sneezing or coughing.

Common ways that HBV can spread are:

• Sexual contact. You may get hepatitis B if you have unprotected sex with someone who is infected. The virus can pass to you if the person's blood, saliva, semen or vaginal secretions enter your body.
• Sharing of needles. HBV easily spreads through needles and syringes contaminated with infected blood. Sharing 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. However, the newborn can be vaccinated to avoid getting infected in almost all cases. Talk to your doctor about being tested for hepatitis B if you are pregnant or want to become pregnant.

Acute vs. chronic hepatitis B

Hepatitis B infection may be either short-lived (acute) or long lasting (chronic).

• Acute hepatitis B infection lasts less than six months. Your immune system likely can clear acute hepatitis B from your body, and you should recover completely within a few months. Most people who get hepatitis B as adults have an acute infection, but it can lead to chronic infection.
• Chronic hepatitis B infection lasts six months or longer. It lingers because your immune system can't fight off the infection. Chronic hepatitis B infection may last a lifetime, possibly leading to serious illnesses such as cirrhosis and liver cancer.

The younger you are when you get hepatitis B — particularly newborns or children younger than 5 — the higher your risk of the infection becoming chronic. Chronic infection may go undetected for decades until a person becomes seriously ill from liver disease.