1. Medical Microbiology Chapter 49 Mechanisms of Viral Pathogenesis

2. Viral Pathogenesis Viral replication review Viral replication review Most viruses exhibit a very specific tissue tropism Most viruses exhibit a very specific tissue tropism Cold viruses, influenza, hepatitisCold viruses, influenza, hepatitis Some do not: Herpes Simplex Virus – type 1 Some do not: Herpes Simplex Virus – type 1

3. Viral Pathogenesis The effects of a virus on a cell: The effects of a virus on a cell: Failed infection (abortive infection)Failed infection (abortive infection) Cell death (lytic infection)Cell death (lytic infection) Viral proteins lyse the host cell Viral proteins lyse the host cell Formation of sycytia Formation of sycytia Induction of apoptosis Induction of apoptosis

4. Viral Pathogenesis Infection without cell death (persistant infection)Infection without cell death (persistant infection) Chronic – new viruses produced Chronic – new viruses produced Latent – infection without new virion production Latent – infection without new virion production Transforming – cells divide rapidly Transforming – cells divide rapidly

5. Progression of Viral Disease Steps – Box 49-2 Steps – Box 49-2

6. Viral Disease Different types of viral infections – Figure 49-3 Different types of viral infections – Figure 49-3

7. Epidemiology Important notes: Important notes: Naked viruses resist dryingNaked viruses resist drying Respiratory Respiratory Fecal-oral Fecal-oral Fomites Fomites Enveloped viruses must remain wet for infectionEnveloped viruses must remain wet for infection Body fluids Body fluids Injection Injection transplants transplants