Caused by the hepatitis B virus (HBV), hepatitis B is a liver infection transmitted when blood, semen, or another body fluid from someone infected with the virus enters the body. This can happen from mother to baby at birth; through sexual contact; sharing needles, syringes, or other drug-injection equipment.
For some people, hepatitis B is a short-term illness but for others, it can become a chronic infection. Age at infection greatly impacts the risk for chronic infection. Approximately 90% of infected infants become chronically infected, compared to 2–6 percent of adults.
Chronic hepatitis B can lead to serious health issues such as cirrhosis or liver cancer. Getting vaccinated is the best method for preventing hepatitis B.