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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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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 Fraction that get sick!
Humans are the most important reservoir of human infectious disease. Pathogen Reservoirs
The Broad Street Pump. Cholera! Common-Source Outbreak
The Broad Street Pump. Common-Source Outbreak Individual cases of (deaths from) cholera.
Common-Source Outbreak Sewage contamination of drinking water.
Propagating Epidemic Epidemic spreads via multiple sources.
Pandemic Index case.
Zoonoses are Human Diseases with Animal Reservoirs. Zoonoses
Toxoplasmosis Zoonoses
Contact Transmission Rhinovirus?
Direct Fecal-Oral Transmission Giardiasis in daycare centers.
Indirect-Contact Transmission Methicillin-resistant Staphylococcus aurius (MRSA)? Beddings are an example of a Fomite, an inanimate object that can transmit pathogens between people.
Indirect-Contact Transmission Influenza virus? Door knobs are another good example of a fomite.
Droplet Transmission Less than one meter Measles?
Airborne Transmission More than one meter Mycobacterium tuberculosis?
Airborne Transmission Contact with air from small room containing 12 people. Contact with air from clean, empty room.
Waterborne Transmission Cryptosporidium parvum?
Waterborne Transmission Giardiasis from water.
Foodborne Transmission Hepatitis A
Foodborne Transmission Balantidium coli
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.
...is pretty crappy at dealing with cause and effect when associations are subtle. Epidemiology Do power lines really cause cancer? What about cell phones?
...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?
Types of Epidemiological Studies A.k.a. analytical
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
Just worry about top three and not about percentages. Relative Nosocomial Frequencies
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.
