| 'Scientific discipline studying the incidence,
distribution, and control of disease in a population - Includes
the study of factors affecting the progress of an illness, and,
in the case of many chronic diseases, their natural history
~ Sleepnet.Com' |
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| There are really two different HIV/AIDS
epidemics, the one found in the US and Western Europe, and the
other affecting developing countries. While these epidemics
share many factors in common, there are important differences
including modes of transmission, rates of spread, groups involved,
and possibly the virus strains. |
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| There are two different human immunodeficiency
viruses: HIV-1
and HIV-2.
HIV-1 causes more severe disease and effects many more people.
Unless otherwise stated, all references to HIV and AIDS will
refer to HIV-1. |
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| HIV entered into human populations in central
Africa. Although it is not known how recently this event occurred,
it is clear that the emergence of HIV into wider populations
was the result of recent trends in urbanization and modern transportation
(e.g. Via truck drivers). Retrospective analyses of stored sera
have documented the presence of HIV infection in Africa from
as early as 1959. By the early to mid-1970s, several studies
have documented seroprevalence
rates of approximately 1% in ordinary populations in Zaire. |
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| There are few known monkey (simian) viruses
closely related to HIV-1, although there are SIV closely related
to HIV-2. It is thought that HIV was transferred from monkeys
to humans. |
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| Other "theories" of the origin of HIV include
germ warfare, vaccine trials, and even more bizarre suggestions. |
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| HIV/AIDS was first described in 1981 as
"the gay men's disease" in two reports, one describing immunodeficiency,
the other Kaposi's
Sarcoma. Shortly thereafter it was recognized in IV drug
users. |
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| Patterns of disease suggested an infectious
agent, but other theories were promulgated, including drug use,
and immunology hypersensitivity. Human disease vectors rapidly
spread the disease, e.g. "Patient
Zero" - sexual promiscuity among homosexual males and shared
needles were important in the expansion of the disease. |
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| By the mid to late 1980s the disease began
to spread to secondary contacts of high-risk groups, especially
the female sexual partners of bisexual and IV drug-using men.
In the 1990s the fastest growing group of HIV-related individuals
is women and children. |
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| At the current time seroprevalence rates
are approximately 0.01 to 0.1% in the total US population. An
unanswered question is whether AIDS will break out of the high-risk
groups and their secondary contacts and subsequently enter the
general population as a sexually transmitted disease. |
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| At the end of 1996, breakthroughs in the
treatment of AIDS led the media to proclaim "the end of the
AIDS epidemic". This was clearly premature. Drug resistance
and treatment failures are becoming important problems. |
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| The characteristics of the AIDS epidemic
in the developing nations are considerably different, where
much more rapid spread and heterosexual transmission are the
norm. High-risk groups, including prostitutes and IV drug users,
exist within the general population and have served to spread
HIV infection. While HIV infection is focused in urban areas,
infection is rising most rapidly in rural areas. |
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| AFRICA - The period of most rapid
spread of HIV infection in Africa was in the 1980s. By 1990,
as much as 20% of the general population and 30% of the urban
population was HIV-infected in some countries, including Malawi,
Rwanda and Uganda. |
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| ASIA - During the past decade, HIV
infection has exploded in Asian countries. At present, Thailand
and India have large populations of HIV-infected individuals,
while China and Burma are lagging several years behind but showing
virtually identical patterns of infection. |
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| Figures in Thailand demonstrate the spread
of infection: in 1988 there were approximately 12,000 infected
individuals and 18 reported cases of AIDS, by 1993 the figures
were 700,000 infections and 8,000 AIDS cases. In India, seroprevalence
among attendees of an STD clinic has risen from less than 5%
in 1988 to 40% in 1993. |
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| The epidemic in India may have several
foci: prostitutes in Bombay and Goa, IV drug users in NE India.
Whether the HIV epidemic will spread to other nations, such
as the Philippines and Indonesia, is a matter of concern and
conjecture. |
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| Latin American and Caribbean - Haiti
was one of the original foci of the HIV epidemic. Brazil is
the most severely affected in South America. |
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| Upon isolation, HIV can be broken down
into different families, or clades, based on degrees of similarity
of genetic sequence. Using these relationships as an epidemiological
tool, one can determine how the infection has and could probably
spread. All HIV types are found in Africa. HIV in Europe and
North America are closely related. HIV in India would be different
from HIV that would manifest in Thailand. |
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| Differences in viral strains may lead to different
modes of transmission. |
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| Global
summary of the HIV and Aids epidemic, December 2004 |
| Global
estimates for adults and children end 2004 |
| Number
of new HIV infextions, AIDS cases and AIDS death by gender per
year reported in Malaysia (1986 - June 2004) |
