The main routes of HIV transmission are sexual, blood-borne and mother-to-child transmission. From a global perspective, sexual transmission is the main one. From the point of view of HIV, the condition that requires the highest efficiency for its transmission is, of course, directly through the blood. Because HIV is the highest in blood, its concentration is the highest, so direct transmission through blood is the most efficient. If the contact is with skin, it will not cause transmission; if it is with mucous membrane, unbroken mucous membrane, the possibility of transmission will rise slightly; if it is with broken wound or mucous membrane, the efficiency of transmission will increase even more; if the blood of AIDS patients is injected directly into other people’s blood circulation system, this is the most efficient way to transmit AIDS, which is from the perspective of AIDS. This is from the perspective of AIDS. Therefore, in practice, AIDS is not easy to spread, and kissing or shaking hands with AIDS patients will not lead to the transmission of AIDS.