1, percutaneous transmission, including transfusion of blood, plasma or other blood products without strict screening, hemodialysis, needles and syringes for injection, examination or surgical instruments (such as obstetrics and gynecology, surgery, ophthalmology, stomatology instruments, etc.), acupuncture needles, etc., not to do “a sterilization” caused by medical transmission, and through small mucous membrane wound Transmission, such as tattoos, earring piercing, accidental stab wounds by medical machinery with blood, etc. Foreign experiments have proved that HBV carriers of 10-4 ~ 10-5 ml of blood, that is, 1/500 ~ 1/5000 drops of blood, injected into the human body will cause hepatitis B, when injecting 1 drop of blood 1/500,000, can cause subclinical infection with HBV. According to another survey in 1983, the HBsAg contamination rate of oral examination and treatment instruments in a dental specialty hospital was 1% to 3%. 2, sexual contact transmission Hepatitis B is classified as a sexually transmitted disease in foreign countries. Epidemiological surveys show that the HBV infection rate of prostitutes, multiple heterosexual couples, male homosexuals is significantly higher than the general population, HBV carrier’s spouse HBV infection rate is higher than other family members. The saliva or semen of HBV-infected people, given to chimpanzees or gibbons subcutaneously or intravenously, can cause HBV infection; the vagina of chimpanzees is treated similarly to sexual intercourse, and then the semen of HBsAg-positive patients is released, which can also cause animals to be infected with HBV. 3, close contact transmission in daily life HBsAg and HBV can be detected in menstrual blood, vaginal secretions, saliva, sweat and other body fluids of HBV-infected patients. 111 cases of chronic HBV carriers in Beijing were investigated, and the detection rate of HBsAg in their saliva with negative occult blood was 39.5%. For HBV-infected patients without a history of vertical transmission and exposure via blood, they may be infected because of close contact in daily life, by inconspicuous skin-mucous membrane breaks, through kissing, communal toothbrushes, facial scrapers, communal teacups eating utensils, etc. The vector of transmission via blood-sucking insects (mosquitoes, bedbugs, etc.) has not been proven to transmit hepatitis B.