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18 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Infection
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The entry and development or multiplication of an infectious agent in the body of animals.
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Contamination
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The presence of infectious agents on the exterior surface of the body or elsewhere, such as water and food.
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Pollution
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The presence of offensive (not necessarily infectious) matter in the environment.
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Reproductive Rate (R)
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The POTENTIAL of an infectious disease to SPREAD between UNITS (animals, pens, herds, regions, countries) within a POPULATIONS.
Describe the average number of secondary cases an infected individual gives rise to during its infectious period. |
Function of:
the RISK of transmission per contact # of infectious contacts per time unit duration of the infectious period and proportion of immune (or infectious) already in the population. |
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R0<1
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Disease will die out.
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Cross-sectional Study
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Looks for risk factors (and measures the association with the disease)
Measures prevalence |
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Cross-sectional Study Disadvantages
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Not for rare diseases
Not for diseases of short duration Difficult to control extraneous variables |
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Cross-Sectional Advantages
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Relatively inexpensive
Allows to study multiple potential causes of disease |
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Cohort Study
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Measures the association of a risk factor with each group (exposed and not exposed)
Followed over time Odds ratio |
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Cohort Study Advantages
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Incidence can be recorded in both groups
Permits flexibility in choosing variables to be recorded |
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Cohort Study Disadvantages
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Requires large numbers of subjects in rare diseases
Long duration of follow up Expensive Difficult to control extraneous variables |
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Case Control Study
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Retrospective study
Looking at hypothesized risk factors in each group Measure of association (Odds ratio) |
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Case Control Advantages
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Good for rare diseases/long incubation periods
Quick to mount and conduct Requires less subjects cheap |
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Case Control Disadvantages
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Validation of accuracy
Difficult to control extraneous variables Selection of appropriate cases and control Incident of exposed and unexposed cannot be determined |
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Prevalence Point
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# cases of a disease existing in a population at point of time/population at that point of time
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How do you calculate true prevalence?
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TP = (AP+Sp-100%)/(Se+Sp-100%)
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Cumulative Incidence (CI)
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Proportion of non-diseased individuals at the beginning of a study that become diseased by end of study
(# of indiv that become diseased during a time period)/(# of healthy indiv in pop at the beginning of that period) |
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Incident Density
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Measures the rapidity with which new cases of disease develop over time
= (# of new cases that occur in pop during a give time period ___________________________ the sum (overall individuals) of the length of time at risk of developing disease |
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