Disease Ecology (Lec 2) study notes

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Health Studies
Caroline Barakat

Disease Ecology (Lecture 2) Agent oBiological oPhysical (high temperature symptoms that can be easily noted) oChemical oPsychosocial oRate of growth opersistence Parasites: organisms that grow, feeds, and is sheltered on or in a different organism and that does not contribute to the survival of its host (Latin: food) o Micro parasites = virus; genetic material engulfed in a protein o Can only survive in a host Virus: ultimate micro parasite; smaller than bacteria and can only reproduce in host Macro parasite: composed of many cells; cycles through transmission stages (eggs/larvae) which pass into external environment Some life cycles are more complicated than others Transmission: passing on harm/affects; movement of a parasite from one host to another Incubation period: interval of time required for development of a disease o Period of activity is detected o Symptoms do not show o Parasite is building within o The higher the period, the higher the outbreak risk Latent period: seemingly inactive period between exposure to an infection and subsequent illness o Pathogen is dormant Parasite virulence: capacity of a parasite to cause disease Zoonotic infection: animal infection that can be transmitted to humans Herd immunity: resistance of a group to a disease due to immunity o Protects from outbreaks Attack rate: ratio of the # of people in whom a certain illness develops/total # of people at risk The 3 main factors that influence the occurrence of a disease - epidemiological triad: Host o Immunity oGenetics nutrition Environment oPromotes exposure for disease to occur Modes of disease transmission: oDirect transmission (person to person) oIndirect transmission (something that is contaminated) Through a common route or vector Contaminated water, air or insect, etc. Portal of entry: oDermal through skin oIngestion through mouth oAspiration through or during respiration o Inhalation airway entry Clinical o Classical, severe oModerate severity | | | | Subclinical oInfection without clinical illness oExposure without infection Determinants of disease outbreaks (# of people immune vs. # of people susceptible Types of disease: o Broad spectrum of disease severity Iceberg concept Totally depends on interaction between host and environment Types of disease outbreaks: 3 main types Endemic = within given geographical area Epidemic = exceeds normal expectancy Pandemic = worldwide epidemic Population growth = more chances of the spread of disease In the past, all diseases were referred to as plagues The sudden increase of individuals that are affected by a certain diseases was once known as a plague "epidemic" is the modern term Greek: epi -> among, demos -> the people Infectious but asymptonic individuals are known as carriers For an infection to persist, each individual on average, must transmit the infection to at least one other individual Highly infectious Usually fatal Potentially life threatening Efficiency of transportation developed Speeds decrease transmission and control Consumption of mean promoted the transmission of parasites Using land exposed people to more parasites o Manure or fertilizer o Industrial revolution o Agricultural revolution o Use of tools Plants Grasses Legumes Fruits/nut trees Fibre crops "Big Five" Sheep Goats Pigs Cows horses Epidemics do not only lose individual lives, but also: Survivors are demoralized They lose faith in customs Material decline Spiritual decline The # of individuals each infected, symbol: Ro, at the beginning of an epidemic The basic reproductive ratio of a disease (or the multiplier of the disease)
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