CSIM - 1.19 - Viruses at Population Level Flashcards
In general terms how do viruses replicate?
ONLY inside host cells
As viruses have a high tun-over rate - which type of viruses have higher intrinsic error rates causing mutations?
RNA viruses
Why do RNA viruses have higher intrinsic error rates causing mutations?
RNA polymerase does NOT have any ‘proof-reading’ capabilities, whereas DNA polymerase does have ‘proof-reading’ capabilities
What are quasi-species?
Predominantly RNA viruses
Due to absent proof-reading, many variants are found within the viral population = “quasi-species cloud” where the mutant spectrum is derived from dominant master-cell
What is viral recombination?
Mainly occurs with RNA viruses
Conservation of required (core) genes and recombination of ‘co-genes’ blocks
What is viral re-assortment - using influenza as an example?
Influenza has 8 separate RNA segments
If two different strains of influenza infect the same host cell at the same time, during replication re-assortment may form a new viral strain with potentially different virulence, resistance and transmission
Give an example of a neuraminidase inhibitor?
Oseltamovir and Tamiflu
Define the term genetic shift?
A major genetic change caused by recombination of genomes
Define the term genetic drift?
Slow accumulation of mutations within a population
What are the origins of HIV.1?
Evolved from SIVcp2 found in chimpanzees
What are the origins of HIV.2?
Evolved from SIVsm found in sooty mangabeys
In relation to disease infection - define the term ‘sporadic’?
Occasional cases of the disease at regular intervals
In relation to disease infection - define the term ‘endemic’?
Continuous occurrence of disease at EXPECTED frequency over a certain time/area
In relation to disease infection - define the term ‘epidemic’?
Occurrence in a region with frequency of illness in XS of normal expectation
In relation to disease infection - define the term ‘pandemic’?
Epidemic across a number of affected countries/continents
