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42 Cards in this Set
- Front
- Back
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Definition of Epidemiology
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Study of distribution and patterns of health-events, health characteristics and the causes or influences in well defined populations
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Define population in Epidemiology
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group of individuals of the same species inhabiting a given area
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Define Health
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Condition in which all vital functions are performed without impairment/within normal ranges
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Define disease
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conditions in which there is impairment of vital functions/not within normal ranges in s/s
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Define Sign
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an objective, measurable manifestation of disease eg. fever, rash, skin color...
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Define Symptom
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a subjective, non-measurable manifestation of disease eg. pain, nausea, fatigue, ringing in ears, anxiety, hunger/thirst
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Causal Agent
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Microbe that causes disease of interest
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Why ID the Causal Agent
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Can lead to measures of control (treatment and prevention)
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3 methods used to ID the causal agent
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1. Use s/s eg. lockjaw=tetanus=C. tetani
2. Collect sample (fecal, blood, mucous) use micro lab testing eg. gram stain, fermentation, IMVic 3. Kochs Postulates to establish link btwn microbe/disease |
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Define occurrence
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Collection of data, use of stats to examine freq/patterns of disease
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3 Statistics used in Epidemiology
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Prevalence
Morbidity Mortality |
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Define prevalence
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How common the disease is over time
# of cases/total pop size x 100% |
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What does prevalence combine?
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Old cases =case in current time period but has had disease since previous time period
New case= case contracted within current time period |
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Define morbidity
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Is disease spreading
morb= new cases/total pop x 100% |
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What does the combination of prev. and morb. tell us?
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Provides rough idea of how long disease may last (based on time period considered)
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Define Mortality
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Tells how likely an indivdual is to die from the disease/how lethal disease may be for given period
# deaths/# infected x 100% |
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4 patterns of occurrence
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Sporadic
Endemic Hyperendemic Epidemic |
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Define sporadic
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disease occurs at irregular intervals with no predictable pattern eg typhoid fever, bacterial meningitis
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Define Endemic
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disease occurs at a low, steady frequency over time in the population eg. cold and flu in non-winter months
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Define Hyperendemic
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disease shows a mild, gradual increase above expected endemic levels eg. colds and flu in winter months
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Define Epidemic
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disease shows a rapid, dramatic increase in freq above expected levels (high # of cases in short time) eg. flu in some years, AIDS
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2 types of epidemic
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Common-Source Epidemic
Propagated Epidemic |
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Define Common-Source Epidemic
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All infected individuals come into contact with the same contaminated source eg. food poisoning, contaminated water supply
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Define Propagated Epidemic
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All cases of disease begin with introduction of one infected individual into pop. (index case), then spreads person-person eg. chicken pox, lice
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6 patterns of occurrence
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sporadic
endemic hyperendemic epidemic outbreak pandemic |
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Define Outbreak
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sudden, unexpected occurrence of disease usually within a small portion of pop. or within limited geographical range eg. ebola, hanta virus
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Define Pandemic
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disease occurs at epidemic levels over large geographical ranges or in large pop. (countries, world-wide)
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Name two types of source/reservoir
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Abiotic - non living sources such as water, soil, food
Biotic - living sources such as animals, humans |
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Most common source of human disease?
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Humans (when humans are cource called "carrier")
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4 types of carrier?
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Active carrier
Convalescent carrier Incubatory carrier Healthy carrier |
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Define Active carrier
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individual has the pathogen present and maybe transmitted to a new host and individual is showing all S/S of the disease
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Define Convalescent carrier
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individual has recovered from S/S but still has pathogen present and may spread to a new host
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Define Incubatory carrier
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individual has pathogen present and may spread to a new host, but is not YET showing S/S
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Define Healthy carrier
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individual has pathogen and may spread to a new host, but will NEVER show S/S
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Mode of Transmission?
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How the pathogen travels from source to a new host
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4 main modes of transmission
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Air-Borne Transmission
Direct Contact Transmission Vehicle Transmission Vector-Borne Transmission |
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Define Air-Borne Transmission
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Pathogen becomes air-borne from the source and travels at least one meter in air to new host
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2 types of air-borne transmission
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1. Droplet nuclei/aerosols - tiny liquid droplets usually from respiratory secretions (sneezing, coughing). Short lived eg flu, measles,TB
2. On dust. long lived (weeks/years) eg staph, strep, anthrax |
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Define direct contact transmission
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requires physical contact between source and new hosts eg. touching, kissing, sex, childbirth (placenta) nursing, ingestion, contact w/ food, water, soil borne pathogens
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Define vehicle transmission
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pathogen travels from source to new host via an inanimate intermediate, FOMITE eg needle, clothes, fork, phone, toilet seat, door knob, thermometer, bedding, towels
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Vector-Borne Transmission
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pathogen travels from source to new host via a living intermediate called a VECTOR eg. mosquito, rodent, ticks, spiders, fleas, flies (smaller-vectors, larger-sources)
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2 types of vector-borne transmissions
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1. external (aka mechanical) vector-borne. Pathogen is carried on the surface of the vector eg. shigella bacteria carried on fly legs
2. Internal (aka biological) vector-borne. Pathogen is carried within the body of the vector, usually in the digestive tracts |
