AIDS, as a contagious disease, has the following three main modes of transmission: one is sexual transmission, the second is mother-to-child transmission, and the third is blood transmission. Measures to prevent AIDS among teenagers should start from the following points: 1. Be clean, do not have sex with high-risk groups, oppose premarital sex, and promote the use of condoms. 2. Do not go to informal medical institutions for cosmetic and other surgeries. 3. Prohibit drug use and do not share syringes with others. 4. Prohibit the use of untested blood products and reduce non-essential blood transfusions. Also do not share razors, toothbrushes, etc.