Introduction to Viruses

Question 1

Explain the basic classification of viruses.

Answer 1

• Host range
• Virion shape
• Presence/absence of envelope
• Genome structure
• Mode of replication

Question 2

Outline the principles of viral culture.

Answer 2

Since viruses require living cells to live, all cultures must take place in cell lines, tissues or intact animals. The cells are grown in a nutrient containing medium, in at atmosphere with 5% CO2.

Question 3

Describe examples of human virus infection of major importance.

Answer 3

- Respiratory
	Influenza A Virus
	Rhinovirus
	Respiratory Syncytial Virus
- Gastrointestinal
	Rotavirus
- Neurological
	Enterovirus
	Herpes Simplex Virus
- Tumours
	Papillomavirus
	Retroviruses

Question 4

Define virion

Answer 4

The complete, infective form of a virus, outside its host cell, with a core RNA and a capsid

Question 5

What are the stages of virus replication?

Answer 5

• Attachment
• Uncoating
• Replication of genomic nucleic acid
• Protein synthesis
• Virion assembly (insertion of virus proteins into a membrane)
• Budding and release

Question 6

What are the methods of viral transmission?

Answer 6

• Blood bourne
• Sexual
• Vertical
• Faecal - oral
• Droplet
• Airborne
• Close contact
• Vector-borne (indirect transmission of an infectious agent - occurs when a vector bites or touches a person - Zoonotic ( a disease that normally exists in animals but can infect humans)

Question 7

What are the consequences of viral infection?

Answer 7

• No, short or long lasting immunity
• Chronic infection
• Latent infection
• Transformation

Question 8

What are the three aspects of a virus that you can detect?

Answer 8

- The whole organism 
	Microscopy 
        Culture
- Part of the organism 
        Antigen detection 
        DNA/RNA detection
        PCR 
- Immune response to a pathogen

Question 9

What is common in all antiviral agents?

Answer 9

They are virustatic none are virucidal. This means they only inhibit the growth of the virus, stops the virus replicating