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 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

Humoral Hypothesis Humor = body fluid Mood, personality are determined by your own individual mix of humors Disruption leads to illness Hippocrates

Restoring the balance of Humors Many things might force the humors out of balance- The 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 19 th 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 19 th 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 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 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 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