Page 6 - AIDSBK23C

Page 6

CHAPTER 1 - HUMAN IMMUNODEFICIENCY VIRUS

INTRODUCTION

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 epidemic 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
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multiple factors. The advent of quick air travel in the 20 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
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of drugs of abuse through injection became more widespread in the 20 century.[2]
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
st
1990's and into the 21 century.[3,4]
Although the HIV infection rate in the United States increased rapidly in the 1980's,
peaked in the early 1990’s, and has declined since, the reservoir of HIV-infected persons
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developing AIDS and requiring therapy continued to increase through the 1990's and into the 21
century. At the end of 2008, estimates of nearly 1.2 million persons living with HIV, including
almost 0.25 million whose infection was undiagnosed, were present in the U.S.[5,6] At the end
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of the 20 century, over 21 million persons worldwide had died from AIDS, over 34 million
were living with HIV infection, and over 95% of HIV infected persons resided in developing
nations.[7,8]
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At the start of the 21 century, the prevalence of HIV infection stabilized at about 0.8%.
However, 95% of new HIV infections and deaths occurred in developing nations, and two thirds
of persons living with HIV infection resided in sub-Saharan Africa. The age group most
affected, young persons from 15 to 24 years of age, accounted for 45% of new HIV infections.
Worldwide, over half the victims of AIDS are women, and a consequence of this is perinatal
infection resulting in a significant number of children born with HIV infection. The scope of the
AIDS pandemic has already led to serious consequences, not only for health care systems of
countries unable to cope with many AIDS victims, but also for the national economies of those
countries because of the loss of young to middle aged who are economically most productive.[9]
Costs for detection, diagnosis, and treatment are considerable when effective therapies
for persons with complications of HIV infection are instituted to prolong survival. In the 1990’s
in the U.S., the average cost for medical care of an HIV-infected patient was double the average