Exposure to air is not particularly harmful because HIV does not spread through the air and AIDS is not a respiratory disease. AIDS is a blood-borne disease that is transmitted through the blood and body fluids of AIDS patients. There are three main modes of transmission, namely sexual, blood and mother-to-child transmission. Sexual transmission is caused by the exchange of bodily fluids through unprotected sexual intercourse. Blood transmission is when the blood of an AIDS patient enters the body of a healthy person in some way and causes infection. Mother-to-child transmission is when a mother with AIDS transmits the virus to her baby during pregnancy or while breastfeeding.