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Chapter 20: Epidemiology PowerPoint PPT Presentation


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Chapter 20: Epidemiology. Important Point:. If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!. Common Terms. Common Terms. Fraction that get sick!.

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Chapter 20: Epidemiology

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Chapter 20 epidemiology l.jpg

Chapter 20:Epidemiology


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Important Point:

If you are having trouble

understanding lecture material:

Try reading your text

before attending lectures.

And take the time to read it well!


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Common Terms


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Common Terms

Fraction that get sick!


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Humans are the most important reservoir of human infectious disease.

Pathogen Reservoirs


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Pathogen Transmission


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Portals of Entry


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Portals of Exit


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The Broad Street Pump.

Cholera!

Common-Source Outbreak


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The Broad Street Pump.

Common-Source Outbreak

Individual cases of (deaths from) cholera.


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Common-Source Outbreak

Sewage contamination of drinking water.


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Propagating Epidemic

Epidemic spreads via multiple sources.


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Pandemic

Index case.


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Pandemic


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Zoonoses are Human Diseases with Animal Reservoirs.

Zoonoses


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Toxoplasmosis

Zoonoses


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Modes of Transmission


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Contact Transmission

Rhinovirus?


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Direct-Contact Transmission


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Direct Fecal-Oral Transmission

Giardiasis in daycare centers.


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Indirect-Contact Transmission

Methicillin-resistant Staphylococcus aurius (MRSA)?

Beddings are an example of a Fomite, an inanimate object that can transmit pathogens between people.


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Indirect-Contact Transmission

Influenza virus?

Door knobs are another good example of a fomite.


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Droplet Transmission

Less than

one meter

Measles?


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Airborne Transmission

More than

one meter

Mycobacterium tuberculosis?


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Airborne Transmission

Contact with air from small room containing 12 people.

Contact with air from clean, empty room.


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Waterborne Transmission

Cryptosporidium parvum?


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Waterborne Transmission

Giardiasis from water.


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Foodborne Transmission

Hepatitis A


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Foodborne Transmission

Balantidium coli


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Modes of Transmission


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Portals of Entry

“Many organisms that cause one disease if they enter one body site are harmless if they enter another, e.g., various enteric urinary-tract pathogens.


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...is pretty crappy at dealing with cause and effect when associations are subtle.

Epidemiology

Do power lines really cause cancer?

What about cell phones?


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...is pretty crappy at dealing with cause and effect when associations are subtle. However...

Epidemiology

What about smoking, a crappy diet, and couch-potato tendencies?


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Types of Epidemiological Studies

A.k.a. analytical


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  • Descriptive studies are simply those that describe the events and rates of disease. They tend to be the first sets of studies done.Quoted or paraphrased from http://dante.med.utoronto.ca/doch/Year1/EPIModule/Part6a.htm

  • Observational/Analytical studies then look towards finding out the causes of the observed rates. They are called "observational" since the epidemiologist does not intervene in the assignment of exposure.

  • Experimental studies are formal research experiments. The classic example is the randomized control trial where one group is randomly assigned a treatment and a control group gets the placebo or "usual" treatment.

  • Experimental studies are expensive and test a very specific question. Usually a great deal of descriptive and observational studies are done first.

Types of Epidemiologcal Studies


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Just worry about top three and not about percentages.

Relative Nosocomial Frequencies


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Nosocomial Infections

2 million acquire and 20,000 die, per-year in the U.S., from nosocomial Infections.

Nosocomial Infections are, by definition, hospital or clinically acquired.


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Nosocomial Infections


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Compromised Hosts


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Compromised Hosts


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Compromised Hosts


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Compromised Hosts


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Compromised Hosts


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Nosocomial Infections


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Exogenous Infections


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Exogenous Infections


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Endogenous Infections


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Antibiotic Resistance


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Nosocomial Infections


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Chain of Transmission


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Universal Precautions


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Universal Precautions


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Universal Precautions


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Preventing Nosocomial Infections


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Preventing Nosocomial Infections


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Link to Next Presentation


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