BIO220H1 Lecture Notes - Lecture 22: Viral Hemorrhagic Fever, Rhinovirus, Drug Resistance

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20 Mar 2020
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March 19th 2020
BIO220 LEC0101
BIO220 Lecture 22: Evolutionary Medicine and Virulence.
Evolutionary Medicine
Definition:
- Application of evolutionary principle into health and disease
Approach:
- Ask why (ultimate) rather than how (proximate) questions
- Why we are susceptible to disease, why do we age? When does drug resistance evolve?
Utility:
- Treatments, preventions, etc.
- Disease requires an ultimate explanation + a proximate explanation to explain why
certain organisms are susceptible/vulnerable to harm stimulus
1) Why are we vulnerable to disease?
a) Trade-off
- There is a cost with certain benefits
- Must balance conflicting demands
- E.g. repair DNA = gives you longevity, but the cost is that all that energy is not used in
reproduction.
- E.g. immune defense = good for targeting pathogens, but it may also target self-body and cause
damage
b) Mismatch with environments
- our environment is changing rapidly, we cannot keep in the pace with the changes thats
happening in the environment
c) Pathogen Evolution
- Pathogens/parasite are evolving fast!! tons of mutation, mass population sizes
- They have tons of variation for natural selection to act on
Virulence Evolution
Ebola Virus
- causes hemorrhagic fever (severe and fatal)
- can be transmitted by direct contact with contaminated surfaces
- symptoms: fever, headache, internal bleeding, chest pains.
- 1976 is the first outbreak of Ebola virus in human
- 88% infected individual died high fatality rate
- ~25 outbreaks in Africa since then, fatality rate varies by countries but still very high
- Ebola is extremely virulent, why?
What determines the severity of pathogens?
- Compare Ebola virus and rhinovirus (normal flu)
- They look different, how can we better explain it?
Virulence = its ability to cause a host to die
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