Hepatitis B virus (HBV) is a contagious infection of the liver. It spreads by contact with the body fluids of someone infected with HBV. Such contact includes having sex or engaging in sexual activity, and sharing drug needles or syringes. Mothers can also pass the infection to their newborns during delivery. HBV infection can cause fever, loss of appetite, nausea and vomiting, stomachache, dark urine, jaundice, and a general feeling of being unwell. These symptoms can be mild or severe. Sometimes, there are no symptoms.
HBV infection can be acute or chronic. Acute HBV infection can incubate in the body for up to 6 months and causes a short-term illness that lasts a few weeks. Sometimes, it can lead to chronic HBV infection. Chronic HBV infection happens when the virus stays in the body. It is a long-term, serious illness that can cause liver cancer, other liver diseases, and other serious health problems. Some people die from chronic HBV infection. The younger a person is at the time of first infection, the higher the risk is of developing chronic infection. Almost 90% of HBV in infants becomes chronic.