The following
are responses and summaries of various readings related to Human Health,
Disease, and the Environment.
Six Modern Plagues: Introduction
Fifty years ago the people of the west believed that humanity
was nearing a point where no longer would we need to worry about sickness. Medicine had developed to a point where it
seemed that it had an answer for every infectious disease in existence. In reality, though, the late nineteenth and
twentieth centuries were merely the calm before the storm. Today new diseases are being discovered at a
rate faster than any previous time in history.
Many of these are diseases which have long existed in other species but
due to humanity’s changing of its environment they are now jumping ship from
their previous bodies to us. This change
is occurring because people are now invading land which they have never before
occupied; forcing bacteria and viruses to evolve and adapt to their newfound
hosts. Evolution usually occurs
naturally over long periods of time but in today’s age the great ecological
change being caused by humans is speeding up this process. Not only are these new diseases on the rise,
but old diseases which have been lying dormant are beginning to re-emerge. Diseases such as small pox and leprosy were
not long ago thought to have been completely eradicated but they are beginning
to return and in strains which the old cures and vaccines have no affect
on. The problem is that the speed with
which our microbial enemies evolve and adapt is increasing and humanity is
directly responsible. Our ever
increasing destruction of natural habitat, invasion of areas where we have not
previously inhabited, and shift from a sedentary lifestyle to daily
transcontinental travel is merely speeding up this process. A change in dominators has already
begun. We will lose the ability to regain
upper hand if we do not soon change our ways.
Disease Basics
A disease is any condition which can cause negative change in
a system. Diseases are often the result
of actions by some other living organism.
These organisms’ (bacteria, viruses, fungi, protozoa, helminthes, and
prions) only desire to reproduce, as is the goal of all living organisms. A disease, or pathogen, invades a host (in
this case a person)via transmission from a vector (carrier), direct contact
with the agent, or acquisition through air or water or other similar
medium. Most pathogens make permanent
home, reservoir, in an agent without ever damaging the system or being
transmitted to another host. When a
pathogen is introduced into a system it is thereafter considered an
antigen. Antigens illicit a response
from the immune system of the host. Once
in the system, antibodies, proteins, begin to be produced which will identify,
neutralize, tag or destroy the antigen.
The dose response is the level of response by the immune system cause by
differing amounts of antigens. Often
times a system may have obtained immunity, enough biological defenses to avoid
infection or disease, through genetic inheritance or a previous encounter with
the pathogen. Herd immunity occurs when a significant portion of a population
has obtained immunity from a pathogen (such as polio or small pox in late 20th
century America). Immunity does not
imply that a similar pathogen will not be effective later on. Pathogens are living organisms which are able
to evolve just like others. Pathogens,
however, often evolve at a much faster rate due to their usually high
reproductive rates, enabling for genetic mutations to occur more often.
Why This Class
New diseases are emerging or old diseases re-emerging due to
human activity causing change in the environment. In the 1970s, when global travel
was starting to become so easily accessible, the emergence, resurgence, and
redistribution of once secluded diseases began to occur. Since 1980 over thirty new emerging diseases
have been identified: these are diseases that had not previously existed, or at
least had not yet been encountered by significant populations of man. These diseases have appeared on the radar due
to man’s change in its interaction with the environment. Alternation or contamination of the
environment by man can lead to new disease or health concerns (mans destruction
of the ozone leads to a greater risk of UV radiation, which may cause skin
cancer and other ailments, and has also caused a rise in malaria related deaths
possibly related to an increase in the global temperature). Because humans evolve slowly over thousands
of years their connection of species of pathogens from Asia to America enable
the pathogens to evolve at a much faster rate than normal therefore leaving
humanity and other much slower evolving organisms at risk. The increased density of human populations
does not help with the disease problem.
A greater population in a smaller area makes communicable diseases all
the much more dangerous. It is necessary
for the environment, climate, etc. to change over time on our planet for the it
to continue to function, but our actions are causing the change to occur at a
much faster rate than nature had intended and it will eventually catch up to
us.
Internet
HIV originated from chimpanzees in the western part of
Africa. The disease evolved from the
simian immunodeficiency virus which occurs in species very closely related to
man. Chimpanzees currently infected with
SIV may, which do not show sickness, may allow us to find a cure for HIV. Some of the viruses are the result of genetic
recombination in chimpanzees prior to human infection. The original infection of the virus is
believed to have resulted when hunters made contact with the blood of an
infected chimp in western Africa. This
particular species is believed to have contributed to no less than three
cross-species diseases and because they are still hunted may yet cause more.
Smallpox emerged in human populations some time around 10,000
B.C.E. The first outbreak of smallpox is
believed to have occurred sometime between the first century B.C.E. and first
century C.E. The Antonine Plague of
165-180 C.E. is the first likely appearance in great amount of smallpox. In the 20th Century alone smallpox
was responsible for 300-500 million deaths worldwide. The World Health Organization declared in
1979 that smallpox was no longer of concern.
The last case of the disease occurred in 1978 England. Smallpox is the only human disease to have
been completely destroyed.
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