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HLTH 240b (10)
Lecture 2

HLTH 240b Lecture 2: Disease Causation

3 Pages
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Department
Global Health Studies
Course Code
HLTH 240b
Professor
Marney White

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HLTH 240: Epidemiology and Public Health 1/19/17  Disease causation 1. Event, condition, or characteristic that comes before the disease and without which the disease would not occur.  Theories 1. 19 century a. Contagion b. Supernatural c. Personal behavior d. Miasma o Malaria (bad air) 2. 20 century a. Germ b. Lifestyle c. Environmental d. Multi-causal  Historical contributions to life expectancy th 1. 19 : hygiene 2. 20 : medicine 3. 21 :t  Etiology of a disease 1. Sum of all factors contributing to the occurrence of a disease 2. Agent + host + environmental factors  Disease models 1. Epidemiological Triangle a. Interaction of an agent and host in an appropriate environment results in disease b. Host  environment  agent triangle 2. Wheel model a. The hub (host) having a genetic makeup as its core, surrounded by an environment schematically divided into biological, physical, and social 3. Web model a. Complex interaction of factors results in disease  Natural history of disease 1. Progression of disease process in an individual over time, in the absence of intervention a. Susceptibility o Presence of factors o No disease manifestations b. Sub-clinical disease o Presence of pathogenic changes (biological onset) o no disease manifestations c. Clinical disease o Presence of signs and symptoms (clinical onset) d. Recovery, disability, or death  Infectious disease process 1. Chain of disease transmission a. Agent o Possible outcomes of exposure to an infectious agent  Infection: invasion and multiplication in the host  Infectivity: proportion of exposed who becomes infected  Infection rate: infected/exposed  Disease: clinically apparent infection o Pathogenicity: proportion of infected who develop clinical disease  Clinical to cub-clinical ratio o Virulence: proportion clinical cases resulting in severe clinical disease  Case fatality and hospitalization rate o Immunogenicity: infection’s ability to produce specific immunity b. Reservoir o Organism or habitat in which infectious agent normally lives, transforms, develops and/or multiplies c. Carrier: individual who does not have apparent clinical disease, but is potential source of infection to other people o Incubatory carriers: transmits disease during incubation period  Infection is present, but not enough for illness  Measles, mumps o Convalescent carriers: transmit disease during convalescent period  Infection is present, but not enough for continued illness  Typhoid fever, com
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