Hepatitis B is a common infectious disease in Hong Kong. It is mainly transmitted by infected blood or body fluids gaining entry into a person's body, such as sharing a needle and syringe among intravenous drug abusers, ear piercing, tattoo or through unprotected sexual intercourse. An infected mother can also transmit the disease to her new born baby.

In Hong Kong about 8% of the population are chronic Hepatitis B virus carriers. Although they are infected, most of them show no symptoms of the disease nor can its presence be detected by a blood test. Hepatitis B virus antigen is detected in the blood and therefore they are called "healthy carriers". One quarter of these carriers will subsequently develop chronic Hepatitis, and they are more prone to develop cirrhosis of liver and liver cancer. For people who have never been infected, it is advisable to receive Hepatitis B vaccination to ensure immunity. Blood tested positive for Hepatitis B surface antigen is discarded and the donor is informed of the test result and advised not to donate again.