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Viral Pathogens and Genetics - Coggle Diagram
Viral Pathogens and Genetics
Pathogenesis
Entry
Respiratory tract
Most common route of viral entry
Enters via aerosols and droplets
We have mechanical and cellular barriers to infection
GI tract
Can easily get in through ingestion
Extremely hostile environment for viruses, so need to be stable
Skin
Viruses need to enter through breaks in skin
Spread within host
Definitions
If it can move with in the body it is called a disceminated infection
If many organs are infected it is called a systemic infection
If a virus can't move within the body it is called a localized infection
Hematogenesis
Most effective, rapid and common means of dissemination
Neural Spread
Enter one axon at the synapse and travel in a retrograde direction towards the brain
Aspects of disease
Tropism and Virulence
Tropism - Viruses are specific for certain cell types and tissues (and species)
Virulence - The capacity of a virus to cause disease in an infected host
There are genes that affect virulence in different ways
Direct effects of infection on cells
Cell death due to viral proliferation
Cytopathic effect
Abortive infection
The infection basically burns itself out
Persistent infection
no cell death and cells are not altered significantly in their growth habits
Chronic - constant production of virus, long incubation period
Latent - proliferation does not occur, but viral genome is maintained, may have intermittent reactivation
Transformation
Causes new cell growth property in cell
Interaction with immune system
Immune response has greates impact on outcome of infection
Type I interferon
induces an antiviral state
Many viruses just evade the adaptive immune response
Immunopathology
Flu-like symptoms
Cytokine storm
Antibody dependent enhancement (ADE)
Spread between hosts
Horizontal Transmission
Person to person
Vertical Transmission
mother to fetus or mother to breastfeeding child
Zoonotic Transmission
animal to human
Viral Genetics
Mutations
RNA viruses mutate more frequently than DNA viruses - there is basically a mutation in every single replicated strand of RNA virus ever
DNA viruses are more stable, RNA viruses are more adaptable
Recombination
Genomes of two different viruses are exchanged
DNA viruses use homologous recombination
RNA viruses use copy-choice recombination
Reassortment
Segmented RNA viruses mix up their segments to see what happens
A bird flu and a human flu will combine in a pig and viola, we got a new virus doods