HIV is contracted from an infected person’s blood, semen, vaginal fluid, breast milk, saliva and, in very rare occasions, tears. These infected bodily fluids must come in contact with the uninfected persons bodily fluids, specifically blood, to be transmitted, according to the Centers for Disease Control (CDC).
HIV is only able to reproduce itself inside a living host. It cannot be spread outside the body, nor can it maintain its infectiousness for more than a few minutes. It is also sensitive to temperature changes, which are more likely outside the body, as well as to oxygen.
Besides temperature, the survival of HIV outside a host depends on the amount of virus in the body fluid that has been expelled. In a laboratory setting, HIV has been kept alive for as long as 15 days after the body fluid has dried, but this was controlled at a stable temperature and humidity that would be nearly impossible to reproduce in the natural world.
Syringes are one “environment” where HIV can survive, in some cases for several days, since blood is trapped in the needle where it cannot be dried out. For this reason, used needles should be thrown out and not reused, especially by someone other than the first user.
The CDC has conducted several studies on HIV concentrations outside the body. When these concentrations are dried, the virus is reduced by anywhere from 90 to 99 percent over several hours. In these studies, the HIV concentrations are significantly higher than they would be outside a laboratory, making theoretical environmental transmission outside the body nearly zero.
Not one HIV-person to date has been infected via contact with an environmental surface, according to the CDC. A fragile virus, once outside the body, HIV is easily killed by hot water, soap, bleach and alcohol.