Transcript Emerging Diseases

Emerging Diseases
Lecture 1:
Historical Ideas About Infectious
Diseases
1.1 Overview
1.2 Historical Ideas About Infectious Disease
A. Supernatural
B. Humoral
C. Miasma
D. Germs
1.1 Overview: Types of Diseases
• Nutritional or dietary diseases-scurvy, or vitamin
C deficiency
• Genetic diseases-hemophilia
• Behavioral diseases-addictions such as alcoholism
• Mental illnesses-bipolar disorder
• Infectious diseases-you can catch them from
someone or something-BIOL 119 Emerging
Diseases is about this type of disease only!!
1.2: Some Historical Ideas About the
Causes of Infectious Disease
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Supernatural – the anger of the gods
Humoral – balance of body fluids
Miasma - bad air
Germs – microscopic particles called germs
because they can “germinate” like a plant
seed
These four have been historically important.
A. Supernatural origin
of disease?
B. Humoral
• Greek physician Hippocrates formulated
“humoral” medicine or “humorism”
• Body fluids were known as “humors”
• When humors got out of balance-disease
followed
• The four humors were yellow bile, black bile,
phlegm and blood
• They were connected to “elements” earth, air,
fire, water
Hippocrates
Humoral Hypothesis
Humor = body fluid
Mood, personality are
determined by your own
individual mix of humors
Disruption leads to illness
Restoring the balance of Humors
Many things might force the humors out of balanceThe important thing was to restore balance
“bleeding” or “bloodletting” was a key treatment
Used up until about 1900 for almost any ailment
including hemorrhage
There were other treatments to adjust other
humors
Hippocrates is honored as the founder
of the western medical profession
• He lived and practiced around 400 BCE
• Main contribution was the idea that disease
had natural causes-not supernatural
• The first major figure to draw a distinction
between medicine and religion
• Hippocratic medicine is very different from
modern medicine but this was a huge step
forward
C. Miasma
Humorism did not explain everything
well
• For example-it was easy to see that certain diseases
were more prevalent in areas with bad sanitation and
this was hard to explain based on the balance of
humors
• It was proposed that rotting sewage and other
materials gave off a polluted vapor or mist that caused
various diseases when inhaled
• The mist was called a “miasma”
• “Bad air”, “Night air”, “nebula”, “malaria” or “Cold air”
were other names for this horrible agent
• “Miasma” explanation for disease
Disease is associated with bad
air-”miasmas” with a sort of
spiritual component
“Miasmas” resulted from the chemical
breakdown of living material
19th Century cities were a
good place
for this
Sanitarians were
determined to clean
up the cities
Sanitarian ideas were fuzzy
They thought disease resulted spontaneously from
garbage, filth and dirt
Thought chemical interactions produced miasmas and no
host was necessary for miasmas to proliferate
They thought cleaning up was generally a good idea
Some medical people of the mid-1800s agreed
Cleaning up garbage,
sewage and dirt
made a difference!
D. Germ Theory of Disease
Many medical professionals suspected
that something less nebulous than a
miasma was responsible
• The “contagionists” felt that physical things
caused disease-not mysterious vapors
• But this explanation ran into trouble because no
one could see or demonstrate the existence of
these physical things
• Improvements in microscopes and in science
methodology changed all that in the second half
of the 19th Century
Louis Pasteur
Showed that microorganisms always occur in infectious
disease or in spoilage
And that they come from pre-existing microbes
Specific microbes are always associated with
specific diseases
Robert Koch
Anthrax
Koch showed that germs caused diseases
Koch’s Postulates-rules for demonstrating
causation
Endospores very stable
In 1854 Dr. John Snow
halted a deadly cholera
outbreak in London by
preventing contact with
contaminated water
Semmelweis-”The Savior of Mothers”
• Puerperal fever or childbed
fever
• Semmelweis notices higher
incidence when doctors deliver
• Dirty hands or instruments
Lister-Antiseptic Surgery
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Used strong chemicals to kill germs
“Carbolic acid” = phenol = paint stripper
Antiseptics
Significant reduction in
post-surgical complications
Through the work of Pasteur, Koch,
Semmelweis, Lister and many others The
Germ Theory of Disease
Became accepted by scienctific and
medical community around 1900.
The Germ Theory of Disease
is the accepted theory today.
Infectious diseases are caused by
germs!
Why is the Germ Theory of Disease
so successful and so widely accepted?
Because it is based on a lot of evidence
and………
IT WORKS!
Types of Germs and Their Diseases
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Parasites-tapeworms, amoebas, protozoa
Fungi- athlete’s foot, yeast infections
Bacteria-anthrax, syphilis, Staph infections
Viruses- AIDS, cervical cancer (HPV),
influenza
• Sub-viral- Mad Cow, Hepatitis D