Study questions for Topic 8-1

Study Questions for Topic 8 (Viral infections and Pathogenesis)

Infection basics

1. What is an inapparent infection? What is an example? Name five routes of viral entry into the body.
2. Can viruses replicate in the skin? Why or why not?
3. Why are mucosal routes excellent pathways for virus entry?  Describe how a virus enters a mucosal surface and reaches the blood. What is a disseminated infection? A systemic infection?
4. Why does the directional release of virions play a role in the spread? What is viremia? What does it do?
5. What routes of spread do virions take?
6. How do viruses invade tissues from the bloodstream? What is meant by tropism? What dictates it?
7. How are viruses transmitted among hosts?
8. Know the meaning of vertical, horizontal, and germline transmission with examples. What is a reservoir of infection?

Viral infections

Think Big Questions

1. Why do you think the incubation period between HIV infection and AIDS has typically been 10 years or more?
2. Describe four different ways viruses may resist immune responses.
3. State why bacteriophages themselves are harmless to humans but might enable certain bacteria to be more harmful to humans.

Short answer questions

1. Briefly describe at least 6 ways viruses can damage infected host cells.
2. Briefly describe 2 different ways viruses can evade host immune defenses and give an example of a virus that uses each mechanism.
3. Match the following with the list below

_____ Viral infections in which the infectious agents gradually increase in number over a very long period of time during which no significant symptoms are seen.

_____ Viral infections of relatively short duration with rapid recovery.

_____ Viral infections where the virus can be demonstrated in the body at all times and the disease may be present or absent for an extended period of time.

_____ Viral infections where the virus remains in equilibrium with the host for long periods of time before symptoms again appear, but the actual viruses cannot be detected until reactivation of the disease occurs.

• acute viral infection
• chronic viral infection
• latent viral infection
• slow viral infection

4. Give an example of a virus causing each of the following:

• acute viral infection
• chronic viral infection
• latent viral infection
• slow viral infection

5.  Describe how a bacteriophage may in some cases enable a bacterium to become virulent and state 2 examples.

Viruses and cancer

Think Big questions

1. People with chronic hepatitis B have a much higher risk of developing liver cancer. This cancer, however, usually appears after decades of chronic infection. Explain the link between HBV and liver cancer and why, if it does develop, it usually takes so long.

Short answer questions

1. Describe how certain viruses may contribute to the development of tumours by altering proto-oncogenes or tumour-suppressor genes.
2. Name 4 viruses that have been implicated in human cancers.