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infection and defence > diagnosis and surveillance of viral disease > Flashcards

diagnosis and surveillance of viral disease Flashcards

1
Q

what are the three ways we can diagnosis viral infections/diseases

A
  1. direct detection of viral replication so measuring viral load which include viral antigen or viral genome
  2. host immune response to virus so antibody levels
  3. detection of characteristics so examination, history, blood tests etc
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2
Q

why should we diagnose an viral infection

A
  • management
  • prevention
  • research
  • surveillance
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3
Q

how can we detect antigen levels for an active virus infection

A
  • lateral flow tests (immunoassays)- point of care
  • elisa- laboratory
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4
Q

what is the most common antigen we test for in lateral flow tests for covid

A
  • nucleocapsid
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5
Q

difference between laboratory testing and point of care testing

A
  • lab testing (Elisa)= qualitative and quantitive, more sensitive and specific, fast for population
  • point of care testing (lateral flow)= just qualitative, cheaper, no special training required, immediate results
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6
Q

how is qPCR/ real time PCR used in viral diagnosis and surveillance

A
  • PCR used to amplify and quantify viral genetic load
  • allows us to monitor genetic load of virus
  • more sensitive than antigen testing
  • however during infectivity period sensitivity of per and antigen testing is roughly the same
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7
Q

what is the steps of pcr

A
  1. denaturation
  2. annealing
  3. extension
    reverse transcriptase may be used if virus is rna- so virus rna genome is converted into dna using reverse transcriptase before pcr and this is known as rt-pcr
    - also for quantifying the viral genome use a fluroscence
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8
Q

what is next generation sequencing

A
  • sequencing large amount of genetic material all at once
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9
Q

what is in depth in pathogen sequencing

A
  • number of times a nucleotide is sequenced
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10
Q

what is metagenomics

A
  • sequencing all dna in sample
  • does no depend on primers
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11
Q

what is whole genome sequencing

A
  • order of entire genetic sequence of an organism
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12
Q

what is an example of a quasi species

A

HIV

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13
Q

what is phylogenetics

A
  • study of relationships between viruses or other organisms
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14
Q

what is serology

A

study of contents of serum so antigen/antibody

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15
Q

how can serology help us identify timing of infection

A
  • IgM antibody suggests recent infection/active infection
  • IgG antibody suggest not a recent infection
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16
Q

what testing do we tend not to do on acute infections

A
  • antibody testing not useful for acute infections to guide early management
  • mainly use testing which directly measures viral replication
17
Q

what kind of infection do we tend to use IgG test for

A
  • chronic (hepatitis e.g. b (anti hbc, hbs)
  • latent (herpes)
18
Q

what is window period

A
  • time between exposure and infection
  • time between exposure and viral replication
  • time between exposure and antibody detection
19
Q

how long does IgM last for and what is the significance of this

A
  • lasts for 12 months
  • can help us figure out timing of an chronic or latent infection
  • e.g. if IgM antibodies detected suggests they have acquired the infection in the last 12 months
20
Q

how can antibody testing be used to detect between pervious infection and vaccination

A
  • so for hep b vaccination only the surface antigen is injected so only hep b surface antigen antibodies are produced, but if you have previously acquired the infection you would also proudce antibodies for hep b core antigens
  • however for some virus infections antibody testing would not differentiate between infection and vaccination e.g. varicella zoster virus
21
Q

antibody tests not usually useful for “ “ infection reactivation and disease management

22
Q

what testing is required for latent infections to detect reactivation and disease

A
  • qpcr
  • used to quantify viral load
  • increase in viral load suggests reactivation
23
Q

what is maternal infection and neonatal infection

A
  • maternal infection is an infection that affects the mother but sometimes also affects the baby- in mums womb
  • infection of baby
24
Q

what is single flex testing and multiplex testing

A
  • single plex describes single target qpcr
  • multiplex testing describes the ability to test multiple targets during single qpcr- take one sample and test for multiple pathogens
25
Q

what is screening

A

testing in asymptomatic population
- blood product screening, ante-natal screening e.g. screening for hiv in pregnant women

infection and defence (14 decks)

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