Virology

Question 1

What is the basic description of viruses?

Answer 1

Not “alive” but are obligate intracellular parasites that infect all forms of life

Question 2

Name some viruses that have become some of the top killers?

Answer 2

TB
Malaria
Hepatitis
HIV

Question 3

Describe the virus life cycle

9 steps

Answer 3

1) Recognition
2) Attachment
3) Penetration
4) Uncoating
5) Transcription
6) Protein synthesis
7) Replication
8) Assembly
9) Lysis and release

Question 4

What are the simple forms of virions?

Answer 4

• Naked icosahedral capsid
• Enveloped icosahedral
• Naked helical nucleocapsid
• Enveloped helical nucleocapsid

Question 5

What are the types of virus DNA molecules?

Answer 5

• Linear single stranded
• Circular single stranded
• Linear duplex
• Duplex with closed ends
• Closed circular duplexes (with and without supercoils)

Question 6

What are the types of virus RNA molecules?

Answer 6

• Linear, single strand infectious, “positive” strand
• Linear, single strand non-infectious, “negative” strand
• Segmented positive strands
• Segmented negative strands
• Double stranded segmented
• Diploid single strands

Question 7

What are the two shapes of animal viruses?

Answer 7

Non-enveloped

Enveloped

Question 8

What are the sites of virus entry and release?

Answer 8

• Conjunctiva
• Respiratory tract
• Alimentary tract
• Urogenital tract
• Anus
• Arthropod
• Capillary
• Scratch, injury
• Skin

Question 9

Name the parts of the herpes simplex virus

Answer 9

• Envelope glycoproteins
• Tegument
• DNA
• Capsid
• Lipid envelope

Question 10

Regarding viral epidemiology, what are the mechanisms of virus transmission?

Answer 10

• Respiratory or salivary spread
• Formites (eg, tissues, clothes)
• Sexual contact
• Zoonoses (animals, insects)
• Blood transfusions, organ transplant, needle sharing

Question 11

Regarding viral epidemiology, what are the geographical/season effects?

Answer 11

• Presence of cofactors or vectors in environment
• Habitat and season for arthropod vectors (mosquitos)
• School/university
• Climatic conditions

Question 12

What viruses do not have a vaccine as of yet?

Answer 12

HIV
RSV
Rotavirus

Question 13

What are the difficulties that are associated with the design and use of anti-viral drugs?

Answer 13

• Few biochemical pathways, unique to viruses
• Therapeutic index often very low
• Selection of drug resistant mutants
• Many viruses which cause similar diseases have very different modes of replication and may not be sensitive to some drugs
• By the time some symptoms appear, often chemotherapy is too late to make much difference to clinical course of disease

Question 14

Type A influenza exists as what shape?

Answer 14

Spheroidal particles

Question 15

Viruses can only replicate in living cells. Describe the multistep process of the influenza infection

Answer 15

• Firstly the virus has to bind to and enter the cell, then deliver its genome to a site where it can produce new copies of viral proteins and RNA
• They then assemble these components into new viral particles and finally exit the host cell

Question 16

What does an antigenic drift result in?

Answer 16

Small mutations

Question 17

What does an antigenic shift result in?

Answer 17

New strain

Question 18

What is Oseltamivir? What name is it sold under?

Answer 18

An antiviral drug that slows the spread of influenza virus between cells in the body by stopping the virus from chemically cutting ties with its host cell
Tamiflu

Question 19

Symptoms of the flu are caused by what?

Answer 19

Huge amounts of proinflammatory cytokines and chemokines 9such as interferon or tumour necrosis factor)

Question 20

Define mitigation

Answer 20

Focuses on slowing but not necessarily stopping epidemic spread reducing peak healthcare demand while those most at risk of severe disease from infection

Question 21

Define suppression

Answer 21

Aims to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely