Human Immunodeficiency Virus (HIV) was first isolated in 1983, called AIDS in it's later stages it is transmitted through the exchange of blood, semen and vaginal fluids and is most commonly contracted via unprotected sex with an infected partner, this leads to the condition known as AIDS.
Once inside the body HIV invades cells (typically those of the immune system) and uses the cells own mechanism of reproduction to re-produce in vast numbers inside the cell.
Eventually the cell becomes so packed with newly formed viruses that the cell bursts spreading the viruses and destroying the cell. As the infection spreads throughout the body the number of destroyed cells increases resulting in the characteristics recognised in HIV patients.
Currently the number of estimated cases of HIV infection worldwide in adults is approximately 32 million and in children, 1 million are known to be infected. The numbers of new cases each year are declining in the United States and Western Europe. However, some areas of Africa have an increasing number of new cases each year with as high as 10 % infection of an entire population in some areas.
There are several forms of HIV, with some forms more prevalent in different regions of the world than others making production of a vaccine difficult.
Additional medical conditions: