Textbook Notes (280,000)
CA (160,000)
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HLTB21H3 (100)
Chapter 1

Chapters 1, 2, 3


Department
Health Studies
Course Code
HLTB21H3
Professor
Caroline Barakat
Chapter
1

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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
Virusultimate mirco-parasitesmaller than bacteria; neither cells not organism; can only reproduce with their host
Marco-parasitescomposed of many cells; cycles through transmission stages (eggs and larvae) which pass into the external
environment
Transmissionmovement of a parasite from host to host
Incubation periodinterval of time required for development of a disease
Latent periodseemingly inactive period between exposure to an inflection and subsequent illness
Parasite virulencecapacity of a parasite to cause disease
Zoonotic infectionsanimal 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 transmissionfrom person to person Indirectthrough a common rate/vector eg. Contaminated water/air
Portal of entry:
Dermalthrough the skin eg. Fungus Ingestion through the mouth eg. E.coli in water Inhalationduring respiration eg.
Particulate matter Aspirationairway entry
Types of diseases:
-broad spectrum of disease severity iceberg concept
Tuberculosisinfectious disease that most commonly attack the lungs
Measles common skin rash, transmitted from respiration
Rabiesaffects central nervous system, transmitted through saliva
Types of disease outbreaks:
1.endemic usual occurrence of a disease within a given geographical area 2.epidemicoccurrence of a disease in excess of
normal expectancy 3.pandemicworldwide 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 immunityresistance of a group to an disease attack due to immunity incubation period
Attack rateratio of the # people in whom a certain illness develops/total # people at risk
Definition of plagues
-highly infectious, usually fatal epidemic disease
-serious, potentially life-threatening infectious disease that is usually transmitted to humans by the nites of rodent fleas
Plagues of Antiquity
-5000 BC to 700 AD
-characterised by parasites with long lived transmission stages
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