Hepatitis B, or viral hepatitis B, is a systemic infectious disease caused by the hepatitis B virus (HBV), which mainly damages the liver. Therefore, hepatitis B can be transmitted, but its transmission requires both the source of infection, transmission channels and susceptible people. Sources of infection: mainly patients with acute and chronic hepatitis B and virus carriers. Acute patients are infectious at the end of the incubation period and during the acute phase, while chronic patients and carriers are more significant as a source of infection. Transmission routes: (1) mother-to-child transmission: mainly includes intrauterine infection, perinatal transmission, and postpartum transmission. Intrauterine infection is mainly acquired through the placenta and may be associated with slight abruption of the placenta during pregnancy. Perinatal transmission or the delivery process is the main mode of mother-to-child transmission, where the infant is infected by contact with maternal blood, amniotic fluid or vaginal secretions from broken skin or mucous membranes. Transmission after delivery is mainly due to close contact between mother and baby. (2) Blood and body fluids transmission: HBV content in blood is very high, a small amount of contaminated blood into the body can cause contamination, such as blood transfusion and blood products, injection, needle stick, sharing razors and toothbrushes, hemodialysis, organ transplantation, etc. can be transmitted. (3) Sexual transmission: unprotected sexual contact with hepatitis B virus-positive people, especially those with multiple sexual partners, have an increased risk of hepatitis B virus infection. Susceptible population: Anti-HBs negative people are all susceptible. Infants and children are at the greatest risk of acquiring HBV infection. High-risk groups include newborns of hepatitis B surface antigen (HBsAg)-positive mothers, family members of HBsAg-positive people, people with repeated transfusions of blood and blood products (such as hemophiliacs), hemodialysis patients, multiple sexual partners, intravenous drug addicts, and medical workers who are exposed to blood. Therefore, hepatitis B can be transmitted, but infection can be prevented by cutting off its transmission route and protecting susceptible people. Therefore, active or passive immunization, better blood management, good personal hygiene and cleanliness are advocated to prevent infection.