About 30% of people who are infected with HBV have no symptoms at all. Children are more likely than adults to show no symptoms. When symptoms do occur, they usually appear within 12 weeks of exposure to HBV and may include:

• loss of appetite
• nausea and vomiting
• weakness
• abdominal pain
• dark urine
• jaundice (yellowing of the skin and whites of the eyes)
• joint pain

When symptoms first appear, the condition is called acute hepatitis. The symptoms usually last for less than six weeks because many people who are infected as adults are able to fight off the infection and recover fully with no lasting effects. However, in some people the infection persists for six months or longer and becomes chronic hepatitis B. Once the infection becomes chronic, it may never go away completely. Chronic hepatitis B develops in 10% to 20% of all people who are infected with HBV but is far more common in infants: 90% or more of infants infected with HBV at birth develop chronic hepatitis while only 30% percent of those infected as children and 5% of those infected as adults do.

Only one-third of people with chronic HBV infection have continuing symptoms. The other two-thirds do not show any symptoms but they harbor the HBV virus and may pass it on to others. The virus may also seriously damage the liver without any obvious symptoms. People with a chronic infection are at very high risk of developing liver cancer or hardening of the liver called cirrhosis, which leads to liver failure and, ultimately, death if a liver transplant is not obtained. Between 15% and 25% of those chronically infected die of liver disease.