AIDS infection must meet four conditions: 1, there needs to be a source of infection, the source of infection is AIDS patients or HIV carriers. 2, the need for a certain number of viruses, a sufficient number of viruses is the necessary conditions leading to the spread of AIDS. 3, the AIDS infection pathway, the most common way of AIDS infection is through the sexually transmitted, and then through the blood, through mother-to-child transmission, no protection measures for sex risk is higher, and the risk of infection is also possible. 4, susceptible people, if the body immunity is more people, more likely to be infected with AIDS. The risk of sexual intercourse without protection is relatively high, and invasive operation in irregular medical institutions or irregular tattoo institutions may also be infected.4. Susceptible groups, if the body immunity is relatively crowded, it is more likely to be infected with the AIDS virus.