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mechanisms by which viruses cause disease - Coggle Diagram
mechanisms by which viruses cause disease
direct effects
cytopathic effects (CPE)
visible damage to host cells
e.g. holes in cell layer
cell death (cytocidal effect)
syncytia formation
inclusion bodies
cell stimulation
poxvirus infected cells
synthesise epidermal growth factors
stimulate cell cycle of neighbouring cells
make them ideal infection targets for viral replication
e.g. poxviruses
orf infection
fowlpox
cell transformation
def
reverse transcription by Retrovirus (RNA-->DNA), viral DNA (provirus) integrates with cellular DNA
1.lead to viral oncogene expression-->tumour formation in host cells
2.disturb morg gene (gene preventing cancer)-->tuour formation
e.g. retrovirus
indirect effects
immune mediated disease
immube cytolysis of infected cells
essential for recovery but damage host
clinical signs often consequence of immune response, rather than the virus itself
immunopathology
antibody dependent enhancement
dengue fever
infected by one strain-->f produce antibody against this strain--> then infected by another strain-->produce antibody that act against the first strain only--> 2nd strain use antibody to replicate and reproduce-->severe illness
why do virus cause pathology
aim of virus= viral fitness, which is the virus' ability to survive and transmit
so virus will do anything to aid its survival and transmission + don't care if host is harmed
thats why pathology may be a side effect caused by virus
generally, virus does not benefit from killing the host
virus X evolve to become more or less pathogenic
only evolve for viral fitness (i.e. evolve to be more pathogenic if doing so aids its survival and transmission)