Geography Reference
In-Depth Information
cent were women. In addition, 460,000 children
died (representing 20 per cent of all deaths).
Unlike many things that we think of as
diseases,
AIDS is not characterised by a set of unique
clinical features common to each patient. It is a
syndrome
—a set of symptoms. The particular set
of symptoms varies from one part of the world
to another. For some regions, there is a
clinical
case definition
that provides a checklist of
symptoms, allowing clinicians to diagnose the
disease.
HIV destroys the ability of the human body to
resist infection. The resulting decline in the
immune system allows certain (often locally
specific) opportunistic bacterial, fungal, protozoal
or viral infections to flourish. It may also allow
the development of some kinds of cancerous
tumour.
The virus is passed between people in blood,
semen and vaginal secretions. Thus it may be
transmitted through infected blood transfusions,
injection syringes, sexual intercourse and between
mother and child at the time of birth. Worldwide,
the main mode of transmission is through sexual
intercourse and to a much lesser, but significant
extent, between infected mothers and their
newborn babies. Other major channels of
transmission are transfusions of unscreened blood
and use of blood products derived from
unscreened sources and use of infected equipment
for injections, including the use of various types
of recreational drugs. The rate of sexual
transmission is increased if people have active
sexually transmitted diseases that result in open
wounds on the genitals.
AIDS affects people in all walks of life.
Unlike leprosy, smallpox or measles, those who
are infected do not show any externally visible
signs. In addition, the disease has a very long
'latency period' during which a person shows
little or no sign of ill-health, can be normally
active, but is also able to pass the infection to
other people. This period ranges from a few
months up to fifteen or even twenty years. A
person may not know that they are infected and
thus may infect many others. For this reason,
whatever number of people with symptoms
appear to the medical services of a country and
are diagnosed as having AIDS, there will most
probably be a greater number who are HIV-
positive. Indeed, the numbers of people who are
diagnosed as having AIDS and being HIV-
positive will depend on the quality and form of
surveillance that exists. This is cost and
administration-dependent, and under-recording
of both is likely to increase with national
poverty, and
vice versa
.
Figure 39.1 shows a projection for an African
country of the relationship between 'normal'
deaths, AIDS deaths and numbers of people in the
population who are HIV-positive and who will
therefore become ill and die within a limited
period.
AIDS AND HIV DISTINGUISHED
In looking at Figure 39.1, we must be careful not
to confuse statements about seroprevalence (the
numbers of people in a population who are HIV-
positive—usually expressed as a percentage of the
population) and statements about the numbers of
people who are actually ill with the disease (usually
expressed as the number per 100,000 of a national
population). It is important to make a clear
distinction between someone being 'HIV-positive'
Figure 39.1
Projected normal deaths, AIDS deaths and
future HIV infections in an African country, 1985-2005.
