HLTA01 Study Guide

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University of Toronto Scarborough
Health Studies
Caroline Barakat

Definitions Parasites organism that grows, feeds, and is sheltered on 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 organisms; can only reproduce within their host Macro-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 infection and subsequent illness Parasite virulence: capacity of a parasite to cause disease Zoonotic infection: animal infections that can be transmitted to humans R0: Reproductive ratio of disease Incidence: newly diagnosed cases Prevalence: combination of new(incidence) and existing cases Low prevalence=low herd immunity Virulence: how quickly and severe a case can be What are the main factors that influence the occurrence of a disease? Host: immunity, genetics, nutrition e.g. person Agent: Biological, physical, chemical. Psychosocial, rate of growth, persistence e.g. bacterium Environment: promotes exposure e.g. contaminated water Modes of Disease Transmission - Direct transmission - from person to person - Indirect through a common route vector, e.g. contaminated air water, mosquito Portal of entry: - Dermal through the skin, e.g. fungus - Ingestion through the mouth, e.g. E.coli in water - Inhalation during respiration, e.g. particulate matter - Aspiration airway entry Types of diseases Broad spectrum of disease severity Iceberg concept Subclinical disease Exposure without infection Infection without clinical illness(asymptomatic infection) Clinical disease Moderate severity mild illness Classical & severe disease Class A: inapparent infection frequent Tuberculosis infectious disease that most commonly attacks the lungs Class B: Clinical disease frequent; few deaths Measles common skin rash, transmitted from respiration Class C: Infections usually fatal Rabies affects central nervous system, transmitted through saliva Types of disease outbreaks Three main types 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 Determinants of disease outbreaks: Herd immunity resistance of a group to an disease attack due to immunity - For measles estimate that 94% of the population must be immune www.notesolution.com Incubation period Attack rate ratio of the #people in whom a certain illness develops total #people at risk Definition of Plagues Legionnaires Disease - 1976 Peter turner, Philadelphia Fatality rate: 15% Toxic shock syndrome (traced to 1979) Death rate: 4%, gendered, not STD Median age: 22 S.aureus, Mary Benton UCLA SARS(severe acute respiratory syndrome) 64yr old chinese physician, HK, Feb2003 Typhoid Fever Mary Mallon, 1906 Irish immigrant to US Carrier of Salmonella enterica aka Typhi Type 1 Epidemic Require big population Regular series of peaks Disease never completely disappears R0 greater than 1 Type 2 Epidemic Medium pop. Peaks are discontinuous Regular occurrence of cases R0 less than 1 No endemicity Temp. absences of the disease Type 3: small pop. Long period with no disease Cases occur at irregular intervals R0 much smaller than 1 Immunization Measles: 95% Mumps: 90% Rubella:85% R0: 50-100 require 99% Measles: dogs, Rinderpest: cattle, Smallpox: cow, Poxvirus: pigs&fowl, human TB related to bovine TB, HIV:chimps, SARS: civet cats Mosquitoes and flies are vectors of Malaria, yellow fever and African sleeping disease Disease that would affect Hunter gatherers: high transmission rates, macroparasites wo vectos or STDs In 8000BC human pop settled in villages ___________________________________________________ Six Plagues of Antiquity Predominant diseases during hunter-gatherer society Move to agriculture and the emergence of epidemic diseases Emergence of cities - urban life 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 www.notesolution.com
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