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14 Dec 2010
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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
Virus – ultimate mirco-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
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
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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Document Summary

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 mirco-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)

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