viruses Flashcards

1
Q

Describe a viruses size

A
  • 20-300nm
  • visualised under electron microscopy
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2
Q

What shapes do viruses usually have?

A
  • icosahedral
  • helical
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3
Q

Which characteristic of viruses make it use the host cellular machinery to replicate?

A

they are obligate intracellular parasites

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4
Q

Describe the capsid of a virus

A

protein coat that encloses genome and core proteins

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5
Q

Describe the envelope of a virus

A
  • lipid bilayer that surrounds capsid of SOME viruses
  • it contains glycoproteins that form projections
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6
Q

Describe the genome of a virus?

A
  • either DNA or RNA
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7
Q

What are the different person-to-person HORIZONTAL transmission routes for viral infections?

A
  • airborne
  • fecal-oral
  • sexual
  • vector-borne
  • blood
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8
Q

What is the VERTICAL transmission route for viral infections?

A

from mother to child

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9
Q

What is pathogenesis?

A

study of the disease process

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10
Q

What is invasiveness?

A

the capacity of a virus to enter a tissue or organ

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11
Q

What is tropism ?

A

ability of different viruses to infect different cell types

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12
Q

What is virulence?

A

the ability for a virus to cause disease

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13
Q

What are the methods for viral diagnosis?

A
  • direct detection
  • indirect detection
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14
Q

Describe direct detection of viruses?

A
  • detection of the whole virus or parts of it
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15
Q

Describe indirect detention of viruses?

A
  • detection of human antibodies against the virus
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16
Q

What are the possible outcomes of acute viral infections?

A
  • complete resolution and recovery (clearance of virus from the host)
  • chronic infection (persistance of virus in the host)
17
Q

What are the types of chronic viral infection?

A
  • continuous viral replication
  • latency and reactivation
  • invasion of genome followed by vertical transmission
18
Q

What is latency?

A

a unique transcription and translational status of a virus in which the productive replication cycle is silent but can reinitiate

19
Q

Describe continuous viral replication

A
  • continuous generation of infective virions (e.g HIV)
20
Q

What are the ways to prevent airbone viral transmission?

A
  • active immunisation (vaccines)
  • masks
  • social distancing
  • quarantine
  • hand washing
21
Q

What are the ways to prevent fecal-oral viral transmission?

A
  • active immunisation (vaccines)
  • safe water supply
  • safe disposal excreta
  • avoid raw food
  • hand washing
22
Q

What are the ways to prevent HIV infection?

A
  • treatment as prevention (TasP)
  • pre-xposure prophylaxis (PrEP)
  • post exposure prophylaxis after sexual exposure (PEPSE)
  • condoms
  • male circumcision
23
Q

What are the steps of viral replication?

A
  1. Binding between virus and target cell (attachment)
  2. Penetration of virus into host
  3. Enzymatic removal of protein coat and liberation of viral nucleic acid into cytoplasm
  4. Production of viral specific mRNA
  5. Morphogenesis and maturation of new viruses
  6. Release
24
Q

What are cytopathic effects?

A

visible changes/damage to host cells due to viral infection

25
Q

What are the two types of pathogenesis of viral infections?

A
  • direct cytopathic effects (caused by the virus replicating in the host cell)
  • indirect immune-mediated cell death
26
Q

Give examples of cytopathic effects

A
  • cell-cell fusion
  • changes to membrane permeability
  • inhibition of cell transcription/translation
  • induction of apoptosis
  • alterations to cytoskeleton
27
Q

Where does primary replication occur?

A

at the initial site of infection

28
Q

Describe the steps to pathogenesis of viral infections

A
  1. virus must overcome the natural barriers against infection
  2. primary replication
  3. movement to secondary replication sites
29
Q

Describe which natural barriers viruses must overcome to infect

A
  • intact skin
  • mucosal surfaces
30
Q
A