VL23: Evolution of virulence Flashcards
What questions do we have about virulence?
- why are pathogens virulent?
- why are does virulence differ between pathogens?
- Does virulence change over time?
What is the advantage od virulence?
thrive in new environments - evolutionary advantage
has to be connected with transmission, if not: dead
Is there a correlation between infection dose and virulence?
no
How/Why is virulence related to transmission
expect higher virulence with horizontal transmission
expect lower virulence with vertical transmission (parent to child) (has to live long enough to get a child)
Name 3 main hypothesis for virulence evolution
- co-insidental evolution hypothesis
- shortsighted evolution hypothesis
- trade-off hypothesis
What is the Co-incidental evolution hypothesis?
virulence may not be target of selection -> accident
tetanus toxin probably selected for living in soil, virulent in humans
What is the short-sighted evolution hypothesis?
some pathogens live for many generations in a host before transmitting to a new host -> select for within host fitness
(evolution is always short-sighted)
Describe 1 example of short-shighted evolution
kjh
Under which conditions can it be useful for a pathogen to cause harm?
kjh
Estimate virulence rates in e.coli and HIV
e.coli 10^-10 mutation rate (rather similar to human rate)
HIV 10^^-6 high mutation rate, large population, huge variation in 1 patient, some will be better at growing/transmission
What is the trade-off hypothesis?
jkh
Why is HIV1 more common than HIV2?
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Describe the trade-off example Myxoma virus
kjh
Describe an experimental test of virulence evolution?
jn
How was the experimental set-up and how were results measured?
kjh
Hos are transmission and virulence connected?
kjh
How is transmission from vectorborne disease different fom directly transmitted disease?
kjh
Are waterborne bacteria more virulent? Why?
edf
What is the best strategy for sexually-transmitted pathogens?
jkbh
What is the definition of R0?
jkh
On what does R0 depend?
kjhb
What is the relationship between virulence and transmission?
KUHJ
How can you calculate R0?
kjh
What are the complications to the trade-off hypothesis?
- Within host evolution
- When a pathogen infects a new host species
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Summary
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