Viruses Structure, Growth And Taxonomy

Question 1

What are the possible outcomes of virus infection in the cell?

Answer 1

1. Cell death (aka cytolytic or cytocidal infection)
2. Chronic infection (virus proliferates in cell which stay alive and carry on its functions, eg hepB virus. Presence of viruses may or may not interfere)
3. Latency (virus stays in cell dormant but can reactivate when immune system is weak or in case of stress or trauma eg: all herpes viruses, stay in trigeminal ganglion. VZ stays in dorsal root ganglion)
4. Transformation (immortalisation of cell eg: EBV. Make them divide???)

Question 2

What is the cytopathic effect?

Answer 2

Structural changes in host cells cause by viral invasion

Question 3

What virus cause what cancer?

Answer 3

By transformation
EBV= lymphoma, nasopharyngeal carcinoma
EBV transforms B cells leading to Burkitt and Hodgkin lymphoma
Hep B and C = hepatocellular carcinoma
Human papilloma virus = cancer of uterine cervix and other tumours in men
HHV8, HTLV1, SV40

Question 4

What are the routes of entry of viruses into host?

Answer 4

Skin 
Mucosal surfaces (naso, oropharynx, conjuntivae, genital tract)
Respiratory tract 
Gastrointestinal tract 
Placenta

Question 5

How do viruses spread in host?

Answer 5

1. Locally from cell to cell
2. Through lymphatics
3. Via the bloodstream (placenta)
4. Axonal pathway (HSV, VZV, rabies)

Question 6

What are the virus shedding routes?

Answer 6

Skin (vesicles)
Respiratory tract (droplets eg:influenza)
Urogenital tract (semen, vaginal secretions, urine)
Blood (BBV incl HBV, HCV, HIV)
Breast milk