The saliva of AIDS patients is usually virus-free, and even if it contains a small amount of virus, it is not enough to cause infection. A ritual kiss with an AIDS patient will not transmit AIDS, and hugging or shaking hands with a cancer patient will also not transmit AIDS. Only unprotected sexual intercourse with AIDS patients can cause HIV infection through exchange of bodily fluids during sexual intercourse, or through importation of blood carrying HIV. Of course, there are also other ways to indirectly contact the blood of AIDS patients, such as using unsterilized instruments to perform invasive operations, such as teeth cleaning, ear piercing, eyebrow tattooing, etc. Therefore, to prevent HIV infection, we should avoid these behaviors.