Note: this site last updated in 2006
virus particles must enter the body
An article from "The Molecules of HIV" (c) Dan Stowell
The HIV virus is quite fragile - it gets destroyed by sunlight, for example - and this explains why you cannot catch HIV from a sneeze.
Possible ways of catching HIV include:
What do these have in common? They provide a "safe" route for the HIV virus particles to pass from one person to another without being destroyed. Unsafe injections/transfusions transfer the virus more-or-less directly from one person's blood to another's. Unsafe sex can transfer the virus onto the mucosal surfaces in the vaginal or anal passage, and if there is a tear in the mucosal surface the virus may pass through into the blood.
Once the virus is in the body, it next needs to overcome the immune system - and if it does that, then the HIV life cycle can begin and AIDS may eventually develop.
The very best way to beat the AIDS epidemic is to avoid unsafe practices. (Safe sex, safe transfusions, and safe injections are all possible!) Drug therapies are all very well, but prevention is better than cure - for HIV as for anything else.