Lecture 20 Flashcards
Of Direct-contact or Vector viral transmissions which one has optimal transmission and why?
Vector transmission optimizes virulence better because for more benefit (transmission) it has less of a cost (virulence)
What two concepts are associated with Virulence Evolution Theory?
1) host replication must be in a positive relationship w virulence and transmission
2) host is only infected w a single genotype of parasite
(Not entirely relevant/true though)
What is the Tragedy of the Commons? What selection does it result in for multiple infections?
It is associated with multiple infections where benefit (transmission) applies to individual strains but cost (virulence) is shared
(The fitness of a single strain is higher than that overall)
It results in multiple infections selecting for higher virulence (all individual strains that make up a virus have high virulence)
List the three stages in the evolution of virulence
1) accidental infection
2) virulence evolution soon after invasion
3) evolution of optimal virulence
What event does accidental infection often refer to?
Spill over events that introduce pathogens into a new host (usually doesn’t last long)
Define an epidemic
The rapid increase in the number of infected hosts
What is required for a successful invasion? What usually results when an invading pathogen is poorly adapted to its new host?
A successful invasion needs a chain of host-host transmissions
When poorly adapted a pathogen will undergo rapid evolution (ex. Myxoma)
Two important surface proteins on flu bacteria
HA (hemagglutinin): antigen recognized by the immune system
NA (neurominidase): allows viral factors to escape from host cell and spread throughout the body
How does resistance arise?
The formation of new mutations (continuous nucleotide substitution) that causes a virus to evade the immune response
How is a parasite’s fitness defined?
When looking at it’s strain history, a virus is more fit depending on how many strains are produced/related to strains in the future
How is a vaccine made?
WHO gathers info on circulating strains -> strains with the most new mutations/that are the most different are collected -> virus nucleic acid is damaged and rendered inactive -> cultured in chicken eggs -> sent out in flu shots
Define herd immunity
The vaccination of ppl who are not at high risk of influenza mortality to help control infection rates
Types of flu (3)
Seasonal/common flu (respiratory)
Pandemic flu (global outbreak)
Avian/bird flu (transmitted from birds)
Define antigenic drift and shift
Drift: accumulation of small mutations
Shift: re-assortment of RNA segments
How are viral genes transferred?
The virus takes over the machinery of the the host to replicate (performs recombination)
