Hepatitis B is primarily transmitted through blood or injection routes. Any blood or bodily fluids containing the hepatitis B virus, including exudates, wound secretions, amniotic fluid, and blood-containing saliva, can directly enter or penetrate through damaged skin or mucous membranes, leading to transmission. The main routes of hepatitis B transmission include blood transfusion, iatrogenic transmission, mother-to-child transmission, and sexual contact. Routine daily contact generally does not result in significant transmission, but frequent close contact can lead to hepatitis B virus infection. Chronic hepatitis B virus carriers have been found to have surface antigens in their saliva, which is caused by minor bleeding from the oral mucosa. If both parties have intact mucous membranes during contact or kissing, infection will not occur. The possibility of transmission through urine, nasal secretions, and sweat is very low, as the hepatitis B virus is generally not transmitted through sweat.