Term
| what happens in the movie Outbreak? what virus is this based on? |
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Definition
| virus spills over from monkey to humans and rapidly spreads through air transmission and saturates the US in only a few days. this is based on ebola |
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Term
| why is the outbreak virus not realistic? |
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Definition
| realistic regarding spill over events, but not realistic in how fast it spread. a virus with such a high death rate will fade out quickly rather than spread across the entire continent |
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Term
| how is the ebola virus different from the virus in the movie Outbreak? |
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Definition
| ebola is not an airborne pathogen |
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Term
| define virulence. through what two modes does it operate? |
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Definition
| the level of severity of a parasitic disease. opperates by decreasing fecundity or increasing mortality |
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Term
| what are the three phases of the evolution of virulence? |
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Definition
| accidental infections, evolution of virulence after successful invasion, evolution of optimal virulence |
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Term
| describe each phase in the evolution of virulence and give examples of each. |
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Definition
| accidental infection happens when an infection results from a transmission route not normal to the pathogen (dead end). may cause short chain of infection before dying out. rabies and SARS were accidental human infections. evolution of virulence occurs when the pathogen can now be transmitted among hosts. optimal virulence after the pathogen has persisted in the population for a while and found an equilibrium between virulence and transission (example malaria) |
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Term
| how did virulence change in the case of the myxoma virus when it was introduced into European rabbit populations? |
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Definition
| at first myxoma virus was very virulent but after persisting for a while it became less virulent to maximize transmission potential while still maintaining enough virulence. virus spread from fleas |
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Term
| are novel (to a host) diseases always initially virulent? |
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Definition
|
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Term
| why does it seem like novel diseases are always initially virulent? |
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Definition
| we only notice the very bad ones |
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Term
| does low initial virulence have an evolutionary basis? |
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Definition
| cannot say anything from evolutionary perspective. a lot of variation |
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Term
| what is an example of a novel disease with low (no) virulence initially. what happened to it in the long run? |
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Definition
| cowpox is example of novel disease with low virulence. can be used as a smallpox vaccine. |
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Term
| why are vectorborne pathogens so virulent relative to non-vectorborne pathogens? |
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Definition
| vectorborne pathogens can be more virulent because the host does not need to be kept alive or in a healthy condition to spread the disease. the vector will do that for the pathogen. |
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Term
| describe the fig wasp life cycle. |
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Definition
| wasp flies to fig, lay eggs, offspring mature and mate inside fig, females gather pollen and disperse to next fig. |
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Term
| describe the nematode and fig wasp life cycle. |
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Definition
| nematode consumes dead wasp in fig, emerge from wasp body and mate, eggs hatch and infect new wasps that are leaving for next fig. |
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Term
| if only one infected wasp is entering the fig, what type of transmission will occur? what will the fig harbor? |
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Definition
| vertical transmission only. only have one wasp and her direct offspring |
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Term
| if several wasps (infected and uninfected) are entering the fig, what kind of transmission will occur and what will the fig harbor? |
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Definition
| horizontal and vertical transmission can occur. |
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Term
| what is a single foundress brood? |
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Definition
| one waps in a fig and only her offspring |
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Term
| please explain how individual fig wasp reproduction, virulence, the proportion of single foundress broods and opportunities for nematode transmission are related. |
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Definition
| when fewer single foundress broods opportunities for transmission increase so virulence can increase |
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Term
| have fig wasp - nematodes evolved to be more or less virulent over time? |
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Definition
| nematodes evolved to be more virulent over time |
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Term
| how does the diarrheal bacterial disease of humans example/graph relate to the fig wasp story? |
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Definition
| when more transmission is possible more deaths will occur from the disease bc the pathogen can afford to be virulent |
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Term
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Definition
| enhancing one trait at the expense of another |
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Term
| write out the R0 equation for parasites. what is it based on? |
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Definition
| R0=(BS)/(a+d+v) based on trade offs. want a to be zero to maximize R0 |
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Term
| using the R0 equation, describe (in terms of trade-off) why parasites evolve towards an 'intermediate' optimal virulence. |
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Definition
| if alpha is too high the hosts die too quickly and hurt transmission oppotunities. if alpha is too low the hosts will recover too quickly and lead to weak transmission |
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Term
| between two vectorborne infections, if one vector is less efficient, how does this affect virulence? |
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Definition
| less efficient vectors decrease virulence bc fewer transmission opportunities |
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Term
| what is an ESS? what does it mean? |
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Definition
| evolutionary stable strategy means you have a genotype that cannot be invaded by any mutant |
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Term
| what is the red queen hypothesis? |
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Definition
| stability and equilibrium do not mean static. organisms must coevolve to maintain evolutionary footing |
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Term
| summarize the trade-off model? |
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Definition
| there are links btw traits that constrain the evolution of virulence (virulence vs. transmission rate or recovery rate) |
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Term
| what are problems with the trade-off model? |
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Definition
| trade off model explains evolution to intermediate virulence but this is not always the case. level of virulence often a function of interaction btw host and parasite |
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Term
| do pathogens evolve to become more or less virulent (6 bil dollar question) |
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Definition
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Term
| what caused the most devastating pandemic in recorded history? |
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Definition
|
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Term
| describe the flu epidemic? when, how many americans, how many people, compare to bubonic plague (black death)? |
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Definition
| 1918, 675,000 americans, more people in one year than four years of plague |
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Term
| define antigenic drift and antigenic shift. what evidence do we have that antigenic shift is the culprit behind major flu epidemic? |
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Definition
| antigenic drift is mutations arising in genome. shift is recombination that occurs within a host |
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Term
| how have changes in pig farming practices spurred the evolution of new swine flue viruses (via what reassortment mechanism?) |
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Definition
| pigs can harbor avian and human viruses. they can recombine together via antigenic shift |
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