AIDS stands for “Acquired Immune Deficiency Syndrome”. It is caused by a virus called “Human Immunodeficiency Virus”, or HIV.
HIV is incapable of causing direct symptoms, but once the virus enters the body through blood vessels, they will begin to attack the “T4 Lymphocytes” (white blood cells and macrophages) reside within the immune system, weakening the immune system’s ability to self-repair. Meanwhile, some harmless disease such as pneumocystis pneumonia (PCP), which normally do not affect healthy person, begins their infection and thus turning HIV positive individual into AIDS patient. Currently, there is no definitive effective cure that can completely eradicate HIV virus, yet several adopted treatments have greatly expanded AIDS patients' life expectancy and quality of life.
HIV exists within the carrier’s bodily fluids, such as semen, blood and vaginal prostate secretory, which the infected person can infect other people through bodily fluid transmission. Besides, the virus count of HIV exists in saliva, sweat, tears and urine are insignificant to cause infection.