AIDS, an acronym for Acquired Immune Deficiency Syndrome (also known as SIDA in romance languages), is a fatal disease which affects the human immune system and its ability to fight infections. Because it is a viral disease as opposed to a bacterial one, there are no available drugs or alternative methods of curing AIDS just methods of treatment for the symptoms.
AIDS stems from the disease HIV (Human Immunodeficiency Virus), a virus which is contracted through bodily secretions such as blood and semen. HIV can be transmitted by unprotected sex (sex without a condom) with an infected partner as well as through any sexual fluid transfer act where a condom is not used both including oral sex, sexual intercourse, and anal sex; the HIV virus can be passed in both heterosexual and homosexual couples, although the "gay stereotype" surrounding AIDS stems from the fact that since rectal tissues are extremely fragile mucous membranes (making anal sex one of the easiest modes of transfer for the virus), AIDS spread rapidly though male gay communities once it took hold. HIV can also be transmitted by any needles that have been shared where one party is infected with HIV regardless of the needle's use (injection of drugs, tattooing, piercing, or otherwise). Another method of transmitting HIV which is less common is from a mother to a child when the child is conceived after or during the time when the mother contracts HIV.
It is important to remember that AIDS cannot be transmitted from behaviors such as hugging, most kissing, shaking hands, or behaviors which do not involve contact with bodily fluids. HIV is NOT proven to be transmitted through saliva or sweat. It is recommended that before sexual interaction that one is tested for STIs, especially HIV and AIDS. Unless you are monogamous and know that both you and your partner have tested negative for HIV and AIDS (meaning you DO NOT have them), safe sex should be practiced, as this can also protect against other sexually transmitted diseases.
In terms of body modifications, it is very important that all jewelry, needles, hooks, and other tools that may penetrate the skin or tissue are sterilized and autoclaved. Always make sure when getting a desired modification that all tools used are either new (many artists will take them out of the packaging in your presence) or appropriately sterilized, and that the studio has and uses an autoclave appropriately. Taking these measures will minimize your risk of exposure to these devastating diseases.