Description
The human immunodeficiency virus (HIV) was unknown until the early 1980’s but since
then has infected millions of persons in a worldwide pandemic. The result of HIV infection is
relentless destruction of the immune system leading to onset of the acquired immunodeficiency
syndrome (AIDS). The AIDS pandemic has already resulted in the deaths of over half its
victims. All HIV-infected persons are at risk for illness and death from opportunistic infectious
and neoplastic complications because of the inevitable manifestations of AIDS.[1,2]
Once HIV infection became established in humans, the spread of HIV has been driven by
multiple factors. The advent of quick air travel in the 20th century provided a means for spread
not present in past human pandemics. Urbanization has led to increased numbers of persons at
risk in close proximity. Human sexual practices with promiscuity have included a larger number
of persons in populations around the world. A practical and easily available means for delivery
of drugs of abuse through injection became more widespread in the 20th century.[1]
The AIDS pandemic has evolved over time, with four main phases of evolution. In the
initial phase, HIV emerged from endemic rural areas to spread among urban populations at an
accelerating rate. In the second phase, dissemination occurred and involved definable risk
groups. Behaviors in these risk groups, including sexual promiscuity and injection drug use, led
to the third phase of escalation, which occurred through the 1980’s. A fourth phase of
stabilization has occurred in some regions such as western Europe, North America, and
Australia, where control measures appear to be having a positive effect. However, some regions
such as central Africa and Asia continued to experience escalation of the pandemic through the
1990’s and into the 21st century.