HIV is mainly found in the blood, semen, vaginal secretions, breast milk, and wound exudate of HIV-infected and AIDS patients, and is highly contagious. The presence of HIV in other body fluids, such as tears, saliva, and sweat, is very small and generally does not lead to the transmission of AIDS. Therefore, sexual transmission, blood transmission, and vertical transmission from mother to child are the main ways of transmitting AIDS. If the mother of a newborn is HIV-infected, she should not breastfeed her newborn to avoid giving the virus to her newborn.