HBV infection is prevalent worldwide, but the intensity of HBV infection varies greatly from region to region. According to the World Health Organization, about 2 billion people worldwide have been infected with HBV, of which 350 million are chronic HBV infected, and about 1 million people die each year from liver failure, cirrhosis and primary hepatocellular carcinoma (HCC) caused by HBV infection. The 2006 National Hepatitis B Epidemiological Survey showed that the HBsAg carrier rate in China’s general population aged l-59 was 7.18%, and the HBsAg in children under 5 years old was only 1%. According to this projection, the existing chronic HBV infection in China is about 93 million people, including about 20 million cases of chronic hepatitis B patients. The prevalent HBV serotypes in China are mainly adrq+ and adw2, and a few are ayw3 (mainly seen in Xinjiang, Tibet and Inner Mongolia Autonomous Region). HBV infection in the central and eastern regions of China is dominated by C and B genotypes (c genotype predominates in the north and B genotype predominates in the south), while D genotype predominates in the western region, especially in Xinjiang, and A genotype is rare. HBV is a blood-borne disease, mainly transmitted through blood (transfusion and blood products, broken skin and mucous membranes), mother-to-child and sexual contact. Due to strict HBsAg screening of blood donors, HBV infection caused by blood transfusion or blood products has been less frequent; transmission through broken skin and mucous membranes is mainly due to the use of medical devices that have not been strictly sterilized, invasive medical and surgical operations, unsafe injections, especially drug injections; other things such as pedicure, tattoo, earring piercing, accidental exposure of medical personnel at work, sharing razors and toothbrushes, etc. can also be transmitted. Other factors, such as foot surgery, tattooing, earring piercing, accidental exposure of medical staff, sharing of razors and toothbrushes, etc. can also be transmitted. Mother-to-child transmission mainly occurs during the perinatal (labor) period, mostly from contact with the blood and body fluids of HBV-positive mothers during delivery. HBV is not transmitted through the respiratory and digestive tracts, so daily study, work or living contacts, such as working in the same office (including sharing office supplies such as computers), shaking hands, hugging, living in the same dormitory, eating in the same restaurant and sharing toilets without blood exposure, generally do not transmit HBV. Epidemiological and experimental studies have not found whether HBV can be transmitted by blood-sucking insects (mosquitoes, bedbugs, etc.).