Lecture 6 Flashcards
How does evolution happen?
- A mutation forms within a population
- Selection for the most fit phenotype
True or false: Viruses causes mutation in a population
False
Mutation already existed in population, it was just selected by virus
What is the arms race?
Host and virus need to constantly change to survive
-cant stay in the same place
What is zoonosis?
Transmission of a pathogen into human pop from another species
Why are all the pandemic viruses in humans zoonotic?
Humans cannot defend against viruses from other species since we have not been co-evolving with them
-immune system is not equipped to handle it
Name an specific example of cross-species transmission
HIV
-jumped from monkeys to humans
How did the HIV pandemic happen?
TRIM5alpha is not suited to block infection against HIV since it came from a diff species and did not co-evolve with it
What has evolved on the virus to prevent human Trim5alpha from working?
The capsid protein on the virus
How do viruses have such high diversity in genome?
They have a high mutation rate
What is the optimal viral mutation rate for viruses and humans?
-Viruses: 2 or no more than 3 –>will not replicate
-Humans: 1
What is a quasispecies
-population of evolved viruses
-viruses exist as quasispecies to adapt and help each other
-lots of diversity some are virulent others are not
How do humans create a diverse genetic pool?
Single nucleotide polymorphisms (SNPs) can cause mutations and be selected for them
Example of mutation in humans? And why would this mutation be in the human pop?
Sickle cell anemia
-those w/ homo allele have sickle cell anemia
-even though it is bad, it has selection against malaria
Name 5 emerging viruses
- SARS-COV 2
- HIV
- Pandemic flu
- Ebola
- Zika
What needs to happen in transmission for it to be a pandemic virus?
Spillover and SUSTAINED human transmission
True or false: Every human pandemic virus has originated in another species?
TRUE
What is spillover?
Animal to human (zoonotic) transmission
What kinds of viruses don’t spread human to human and example?
Zoonotic viruses
-animal–>human–>stop
-Rabies, MERS, bird flu
What kinds of viruses spread animal to human to human and example?
Pandemic viruses
-sustained human transmission
-SARS-COV2, HIV, swine flu
What kinds of viruses spread human to human only and example?
Human specific viruses
-Herpesviruses, seasonal coronavirus and flu
True or false: Probability of a zoonotic jump is not proportional to frequency of contact
FALSE
-Probability of a zoonotic jump is proportional to frequency of contact
-the more we come into contact w/ a species the more likely it is to jump
True or false: Probability of zoonotic jump is inversely proportional to phylogenetic distance
TRUE
-more likely to get a virus from a species that is more similar to us because we have similar machinery
What are the 2 big molecular barriers that drive evolution in host and virus?
- Adaptation to entry receptor–>if virus cant get in then non infection
- Adaptation to overcome cell intrinsic immune factors
What can increase the probability of transmission?
-Insects–>mosquitos
-Intermediate/amplifying hosts
Examples of insect borne viruses
-West nile
-Dengue
Examples of intermediate/amplifying host transmission
-HIV
-SARS
-Pandemic flu
What factors facilitate emergence?
- Population growth
- Human expansion into animal territory
- Global traveling/trading
- IV drug. use and sex trafficking
- Lots of immunocompromised individuals
