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Exam Study Guide - DIsease Ecology, Plagues


Department
Health Studies
Course Code
HLTB21H3
Professor
Caroline Barakat
Study Guide
Final

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Disease Ecology
Parasites organism that grow, feds, and is sheltered an or in a different organism and
that does not contribute to the survival of its host
Virus ultimate micro-parasite smaller than bacteria; neither cells not organism; can
only reproduce with their host
Marco-parasites composed of many cells; cycles through transmission stages (eggs and
larvae) which pass into the external environment
Transmission movement of a parasite from host to host
Incubation period interval of time required for development of a disease
Latent period seemingly inactive period between exposure to an inflection and
subsequent illness
Parasite virulence capacity of a parasite to cause disease
Zoonotic infections animal infections that can be transmitted to humans
R0 (reproductive ratio of disease) - how many people one person can affect; # of 2nd
infections expected
Main factors that influence the occurrence of a disease:
1.host (immunity, genetics, nutrition)
2.environment (promote exposure)
3.agent (biological, physical, chemical, psychosocial, rate of growth, persistence)
Mode of disease transmission:
-Direct transmission from person to person
-Indirect through a common rate/vector eg. Contaminated water/air
Portal of entry:
-Dermal through the skin (eg. Fungus)
-Ingestion through the mouth (eg. E.coli in water)
-Inhalation during respiration (eg. Particulate matter)
-Aspiration airway entry
Types of diseases:
-broad spectrum of disease severity iceberg concept
Tuberculosis infectious disease that most commonly attack the lungs
Measles common skin rash, transmitted from respiration
Rabies affects central nervous system, transmitted through saliva
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Types of disease outbreaks:
1.endemic usual occurrence of a disease within a given geographical area
2.epidemic occurrence of a disease in excess of normal expectancy
3.pandemic worldwide epidemic
Type 1 epidemic: large pop. Regular outbreaks; disease never completely
disappears; R0>1
Type 2 epidemic: regular outbreaks; not enough susceptible individuals; R0<1
Type 3 epidemic: irregular outbreaks; long periods of no disease; R0<1
Attack rate: measure of outbreak; ratio of #people with illness/total #people at risk
Determinants of disease outbreaks:
Herd immunity resistance of a group to an disease attack due to immunity incubation
period
Attack rate ratio of the # people in whom a certain illness develops/total # people at risk
Plagues
Definition of plagues
-highly infectious, usually fatal epidemic disease
-serious, potentially life-threatening infectious disease that is usually transmitted to
humans by the bites of rodent fleas
Plagues of Antiquity
-5000 BC to 700 AD
-characterised by parasites with long lived transmission stages
-person to person contact
The Pharaohs plague
-1900 BC
-Nile Valley of Egypt Agriculture and irrigation
-snail fever or blood fluke disease/endemic hematuria/schistosomiasos
-1799-1801 European soldiers of Napoleons army during the invasion of Egypt
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