When a person is first infected with the hepatitis B virus, they are said to have an "acute" infection.

During this time, a person may or may not have symptoms. For those that do, they may have few or very mild "flu-like" symptoms, or in rare cases they may have very severe symptoms requiring medical attention such as jaundice (yellow skin and eyes), abdominal pain, cutaneous eruption, or joint pain.

During an acute infection, which can last up to six months, a person can transmit the virus to others. About 90 percent of adults will recover from the acute stage within a few months of infection, as their bodies develop immunity to the virus and fight off the infection.1 These people will not develop "chronic" hepatitis. Their symptoms disappear (if they have any), they will no longer be able to transmit the virus to others and they typically have no long-term effects of the infection.

For others, their bodies will not be able to fight off the virus, and will develop "chronic" hepatitis, which is a long-term infection of the liver. These persons are called "chronic carriers" and can transmit infection all their lives.

A person has "chronic" hepatitis B if the infection persists for more than 6 months. About 350 million people worldwide have long-term hepatitis B infection.2 Chronic hepatitis B may last for life; however an infected person may have no symptoms. Whether they experience symptoms or not, this person can actively transmit the disease to others.

Infants can contract the hepatitis B virus during birth, and will almost always develop chronic hepatitis.

Those with a chronic hepatitis infection may develop serious liver damage over time. Chronic hepatitis B infected are at higher risk of liver failure and liver diseases such as cirrhosis and liver cancer. In some cases, complications of liver damage causes death.