MGY277H1 Study Guide - Final Guide: Antigenic Variation, Escherichia Coli, Botulism
8 Jun 2018
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Unit 9
Video #1: Epidemiology
Epidemiology- study of disease patterns in populations
- epidemiologists- health detectives
o collect, compile data about sources of disease and risk factors
o design infection control strategies
o prevent/predict spread of disease
o use expertise from ecology, microbiology, sociology, statistics, and
psychology—GLOBAL or FOCUSED
o influences our daily lives (hand washing, waste disposal,
restaurant/food inspection, water treatment)
- Communicable- contagious; spread from one host to another
o Ex; measles, colds, flu
o Transmission determined by interactions between environment,
pathogen, and host
o Control of factors may break infection cycle
- Non-communicable- do not spread from host to host ex; tetanus
o Mostly come from individuals normal microbiota or environment
o Ex; legionnaire’s disease- causes outbreaks and has an infection cycle
that must be broke, doesn’t spread from person to person
Rates of Disease in a Population
- RATES are more important than absolute number of cases
- Attack rate- percentage of people who become ill in population after
exposure
o **Decreases in an immune population
o Reflects infectious dose, immune status of population
- Incidence rate- number of new cases/time/population
o Measure of risk of an individual contracting a disease
- Prevalence- total number of cases at any time for a specific period in a given
population
o Reflects overall impact of disease on society; includes old and new
cases and duration
o /per 100,000- most common
- Morbidity- burden of disease in population at risk
o ex; flu has high morbidity rate (infected can spread to several)
- Mortality- overall death rate in population
o Less developed countries= associates with non-communicable
o Infection is major cause of death in developing countries
- Case fatality rate- % of population that dies from a specific disease
o Plague= high rate
o Rate for AIDS decreased due to improved treatment
- Endemic- constantly present in population (ex; common cold)
- Outbreak- higher than expected cluster of disease cases over a specific time
in population; flare ups in a confined area
- Epidemic- unusually large number of cases- usually over a larger region
find more resources at oneclass.com
find more resources at oneclass.com
o Introduced or endemic disease
[epidemic and outbreak are used interchangeably]
- Pandemic- global (ex; AIDS)
Descriptive Studies
- collect data that characterize occurrence (time, place, individuals affected) of
an outbreak—used to compile risk factors for spread
o person- determine profile of people who become ill
▪ ex; age, gender, ethnicity, occupation, personal habits, previous
illness
o place- geographic location helps pinpoint source
▪ clues to reservoirs, vectors, or boundaries to transmission
o time- season and rate of spread
- following epidemics
o incidence and prevalence can follow different trends
Outbreak Epidemiology
- common source epidemic/outbreak
o rapid rise in case~ exposure to single source of pathogen
o plummets when source is gone
o trace to find out the source
- propagated epidemic- slow rise in cases= contagious disease spreading in
population
o first case= index case or patient zero
- some have features of common source and propagated
Analytical Studies~ determine relevancy of risk factors from descriptive study
- cross-sectional studies- surveys range of people at a single point in time for
prescence/absence of disease
o suggests associations between risk factors and disease, does not
establish cause
- retrospective studies- actions and events following outbreak compared
o case control study- identifies causative chain of events leading to
disease
o developed disease vs. healthy controls
- prospective studies- starts with population of interest that doesn’t have the
disease yet and follows them
o predicts tendency to develop disease
o groups with know exposure to risk factor are selected and followed
Outbreak containment-
- critical to containing an outbreak
- contact tracing- tracking down people who may have been exposedgh
- interview patients and families
- check hospital records for when and where a patient stayed and who was
with them
- inform and monitor contacts for disease
- *care about the source to prevent source from infecting people
Quarantine vs. Isolation
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Communicable- contagious; spread from one host to another: ex; measles, colds, flu, transmission determined by interactions between environment, pathogen, and host, control of factors may break infection cycle. Rates are more important than absolute number of cases. Attack rate- percentage of people who become ill in population after. Rates of disease in a population exposure: **decreases in an immune population, reflects infectious dose, immune status of population. Incidence rate- number of new cases/time/population: measure of risk of an individual contracting a disease. Prevalence- total number of cases at any time for a specific period in a given population: reflects overall impact of disease on society; includes old and new cases and duration, /per 100,000- most common. Morbidity- burden of disease in population at risk: ex; flu has high morbidity rate (infected can spread to several) Mortality- overall death rate in population: less developed countries= associates with non-communicable, infection is major cause of death in developing countries.
