viral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesis

viral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesisviral pathogenesis

1. VIRAL PATHOGENESIS

2. VIRAL PATHOGENESIS The process by which a viral infection leads to disease. This interaction between the virus and the host cell can be viewed at three levels.   1- The effect of viruses on the cells.   2- Disease progression The way in which viruses     spread through the body and cause disease     (from entry till viral shedding ).   3- The immune response to viral infection.

3. EFFECT OF VIRUS INFECTION ON CELL               [THE INFECTED CELL] There are five main effects of virus infection on the host cell:   1- Cytocidal (death of the infected cells).   2- Formation of multi-nucleated giant cell.   3- Formation of inclusion bodies.   4- Transformation of the infected cells.   5- No apparent changes.

4. INCLUSION BODIES RABIES INFECTION OWL EYE- CMV INFECTION

5. SYNCYTIA HIV HSV MEASLES HERPES PARAMYXO

6. MALIGNANT TRANSFORMATION: Infection with certain viruses causes malignant transformation which is characterized by unrestrained growth and morphological changes such as focal area of rounded piled up cells. A hall mark of viral infection of cell is the Cytopathic effect ( CPE). It usually begins with rounding and darkening of the cells and culminates in either lysis or giant cell formation.

7. Cytopathic Effects CPE can take several forms:   1. Cell lysis     2. Cell rounding     3. Syncytium formation     4. Inclusion bodies formation

8. DISEASE PROGRESSION Transmission of virus and entry into the host. Replication of virus and damage to cells. Spread of virus to other cell and organs. Immune response. Persistence of virus.

9. The stages of typical viral infection are Incubation period Prodromal period Specific illness period Recovery period

10. The stages of a typical viral infection: The incubation period Prodromal period The specific-illness period:  The signs & symptoms of viral diseases are the result of Cell killing by   A) Inhibition of cellular macromolecular synthesis   B) Immunologic attack ( Immunopathogenesis)   Cytotoxic T cells e.g. Hepatitis (HAV, HBV,HCV)   Immune complex e.g. arthritis (HBV)   Autoimmune disease 4. the recovery period

11. VIRUS SPREADS IN BODY LOCALIZED INFECTION: * Viral infections are either localized to portal of entry e.g common cold caused by rhino virus. GENERALISED/ SYSTEMIC INFECTION: * Viral infection may spread systemically through out the body e.g poliomyelitis