pathogenesis - ViralPathogenesis Derek Wong...

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    Viral Pathogenesis Derek Wong http://virology-online.com
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Viral Pathogenesis Viral pathogenesis is the process by which a viral infection leads to disease. Viral pathogenesis is an abnormal situation of no value to the virus. The majority of viral infections are subclinical. It is not in the interest of the virus to severely harm or kill the host. The consequences of viral infections depend on the interplay between a number of viral and host factors.
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Outcome of Viral Infection Acute Infection Recovery with no residue effects Recovery with residue effects e.g. acute viral encephalitis leading to neurological sequelae. Death Proceed to chronic infection Chronic Infection Silent subclinical infection for life e.g. CMV, EBV A long silent period before disease e.g. HIV, SSPE, PML Reactivation to cause acute disease e.g. herpes and shingles. Chronic disease with relapses and excerbations e.g. HBV, HCV. Cancers e.g. EBV, HTLV-1, HPV, HBV, HCV, HHV-8
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Factors in Viral Pathogenesis Effects of viral infection on cells (Cellular Pathogenesis) Entry into the Host Course of Infection (Primary Replication, Systemic Spread, Secondary Replication) Cell/Tissue Tropism Cell/Tissue Damage Host Immune Response Virus Clearance or Persistence
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Cellular Pathogenesis Cells can respond to viral infections in 3 ways: (1) No apparent change, (2) Death, and (3) Transformation Direct cell damage and death from viral infection may result from diversion of the cell's energy shutoff of cell macromolecular synthesis competition of viral mRNA for cellular ribosomes competition of viral promoters and transcriptional enhancers for cellular transcriptional factors such as RNA polymerases, and inhibition of the interferon defense mechanisms. Indirect cell damage can result from integration of the viral genome induction of mutations in the host genome inflammation host immune response.
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Skin - Most viruses which infect via the skin require a breach in the physical integrity of this effective barrier, e.g. cuts or abrasions. Many viruses employ vectors, e.g. ticks, mosquitos or vampire bats to breach the barrier. Conjunctiva and other mucous membranes - rather exposed site and relatively unprotected Respiratory tract - In contrast to skin, the respiratory tract and all other mucosal surfaces possess sophisticated immune defence mechanisms, as well as non-specific inhibitory mechanisms (cilliated epithelium, mucus secretion, lower temperature) which viruses must overcome. Gastrointestinal tract - a hostile environment; gastric acid, bile salts, etc. Viruses that spread by the GI tract must be adapted to this hostile environment. Genitourinary tract
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This note was uploaded on 12/27/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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pathogenesis - ViralPathogenesis Derek Wong...

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