HIV-infection can occur all over the world, but not as much in some places as in others. It's a significant problem in sub-Saharan Africa for example; in some countries more than 10% of the adult population is infected with the HIV virus (and they therefore also pose an infection hazard for others).
HIV-infection degrades the body's natural defences, making it vulnerable to all manner of infections, which a healthy immune system could otherwise cope with. We call these “opportunistic” infections and someone who is vulnerable to them has got AIDS. If they are not treated on time these infections are fatal. The HIV virus is transmitted via:
- unprotected sexual contact;
- infected syringes, hypodermic needles, infusions, etc.;
- uncontrolled blood, tissue and organs;
- from mother to child during pregnancy or childbirth.
Nowadays HIV-infections can be effectively treated, but the necessary medication is expensive and in many developing countries it is in short supply. There is no vaccine against HIV. People who are HIV positive are sometimes not allowed to be given certain vaccinations (such as for yellow fever, for example).