Aquired Immmune Deficiency Syndrome - late stage progression of HIV infection. Transmissable through bodily fluid exchange or blood to blood contact. Least concentration in bodily excretory products, low concentration in saliva (and one's own saliva may provide some protection) in vaginal secretions (though still present) highest concentration in semen. Crosses across gender, age and socio-econimic boundaries, though usually more quickly progressing the lower down the ladder the sufferer is, due to lack of access to medical care. On the rise in the 15-24 demographic in the United States. Easily avoidable, but thankfully more and more (in the United States) becoming a "chronic" disease like herpes due to the availability of more and better retro-viral therapies.
The comic Elaine Boosler has said "Wouldn't it be great if you could only get AIDS by giving money to television preachers?"