2. Vial Pathogenesis - Viral Properties Viral Pathogenesis...

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1 Viral Pathogenesis and Viral Pathogenesis and Host Response Host Response Viral Properties Viral Properties • Viruses are intracellular parasites which need living cells to survive and reproduce. • They bind to specific cell receptors – they display cell tropism • They require host cell machinery for viral protein synthesis (to make new viruses) Viral Reservoirs Viral Reservoirs • Some viruses are host specific – Small pox, HIV are specific to humans – A subset of Influenza infect humans • Some viruses can infect multiple hosts – Rabies, SARS (?) Routes of Transmission Routes of Transmission a) Contact with a sick person Direct - genital herpes, colds Fomite (kleenex) - adenovirus (eye infections) Droplet - influenza, chickenpox b) Vehicle (things viruses can travel in) Food - hepatitis A – infected food handler Water – Norwalk virus (causes diarrhoea) c) Vector (insects that spread viruses) Arthropods - mosquito – Dengue, West Nile Encephalitis tick - Rocky Mountain Spotted Fever Portals of Entry Portals of Entry a) Non-intact skin (cuts, eczema) examples: hepatitis B and C, HIV b) Mucous membranes inhaled (respiratory tract) examples: influenza, cold viruses direct contact (splash to the eye or mouth, sexual contact) examples: hepatitis B, herpes, HIV contaminated food, water (GI tract) example: hepatitis A, Norwalk virus c) Parenteral (through the blood) transfusion (West Nile) IV drug use (HIV, hepatitis C) needle stick injury (hepatitis B and C, HIV) Factors determining if Infection Factors determining if Infection Occurs Occurs Viral: – Viral load (number of copies present) – Viral fitness to avoid host immunity – Site of entry – Degree of adaptation to host
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2 Factors determining if Infection Factors determining if Infection Occurs Occurs Host: – Pre-existing immunity due to vaccination or previous exposure – Age (very young and old at greatest risk) – Immune status (HIV and transplants at greatest risk) – Nutritional status (protein needed for immune response) – Genetic factors (HLA and Immunodeficiency) – Pregnancy
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This note was uploaded on 05/09/2010 for the course LMP 232 taught by Professor Crandall during the Spring '10 term at University of Toronto- Toronto.

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2. Vial Pathogenesis - Viral Properties Viral Pathogenesis...

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