A person infected with hepatitis B who can transmit the virus to others is called an “infectious agent”. The size of the infection depends on the level of the virus in the blood, that is, the level of “HBV DNA” detected in the blood. 1, “major triple-positive” chronic hepatitis B virus carriers have active virus replication and high levels of virus in the blood, and are the most active source of infection, especially the “major triple-positive” carriers who are hidden in the population and have not yet been found, and have the highest potential for infectiousness. However, the virus must be transmitted through certain channels (blood as the transmission carrier), and general daily contact is not infectious. 2, “small three positive” chronic hepatitis B virus carriers, almost undetectable virus in the blood, its infectiousness is very low. 3.The size of the transmission potential of the source of infection also depends on his work or lifestyle, and the way he comes into contact with others and the degree of closeness. 4.The size of the infectiousness has nothing to do with the level of transaminase, it is the virus that is infectious, not transaminase. 5, not the more serious the disease is the more infectious, the more serious the disease is due to their own immunity to reduce the level of virus in the body, but its infectiousness has been reduced.