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8 Cards in this Set
- Front
- Back
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What is the basic reproductive number?
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expected number of secondary cases generated by a primary case in an entirely susceptible population
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How is the basic reproductive number interpreted?
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R >1 implies that it will spread
R< 1 implies the infection will die out and not be able to propagate |
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What is the effective reproductive number?
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average number of secondary cases attributable to a single case of infection
- NOT in an entirely susceptible population |
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How does the effective reproductive number compare to the basic reproductive number?
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R= R0(x) where x is the susceptible fraction of the population
It will be smaller because the population is not entirely susceptible |
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How does the susceptible fraction change over time in an outbreak?
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it will decrease as animals either die or recover and gain immunity
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What factors affect the effective reproductive number?
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infectiousness of the agent
number of adequate contacts in the time period duration of the infectious period presence of susceptible animals |
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How does vaccination effect the effective reproductive number?
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It will decrease the effective reproductive number because fewer individuals in the population will be susceptible to infection
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What percentage of the population must be vaccinated to generate herd immunity?
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1-1/Ro
This is often >90% |
