diagnosis of viral infections

Question 1

why diagnose viruses

Answer 1

infection control
management
education
research

Question 2

tests for direct detection of virus replication

Answer 2

viral proteins- antigens
viral genetic material - rna or dna
direct visualisation of viral particles

Question 3

tests for detection of host response specific to infection

Answer 3

antibody- serology
immune cell function

Question 4

tests for characterisation of disease
not specific to infection e.g pneumonia

Answer 4

history
examination
imaging
blood tests
other samples

Question 5

acute infection- short viral replication

Answer 5

sars cov 2

Question 6

chronic infection- viral replication over several months

Answer 6

hiv

Question 7

antigen detection by lateral flow tests are immunoassays

Answer 7

antigen- anything that is recognised and activates immunity
lateral flow test- primary antibody recognises antigen
control line- tests fluid is moving along test strip
when specific antigen binds to antibody, detection test line appears

Question 8

sars cov 2 acute virus infection

Answer 8

nucleocapsid antigen detected
most common antigen in lateral flow tests

Question 9

chronic virus infection hepatitis b virus

Answer 9

virion hbv,
infects hepatocytes.
virus binds to cell and releases capsid
creates magic episome, circular dna within the nucleus
covalently coiled
surface antigen hbsag
protein passed out of cell
dane particle - hepatitis b virus particle
non viral filaments spheres
blood borne viruses tested by blood sample- looking for surface antigen

Question 10

immunoassay

Answer 10

antibody specific to antigen, secondary antibody can bind and flourescence shows

Question 11

laboratory vs point of care testing poct

Answer 11

qualitative and quantitative
fast for population
high sensitivity and specificity
point of care test, fast easy and chea[ compared to labrotary test

Question 12

latent herpes pattern of reactivation
infected for life

Answer 12

episodes where virus activates all of its genes
only use viral load (dna) to test as antigens hang around for too long, doesnt indicate if person is infected

Question 13

qualitative diagnosis- measuring viral genetic material (RNA or DNA)

Answer 13

yes or
good for diagnosis

Question 14

quantitative diagnosis

Answer 14

good for monitoring
viral load monitoring

Question 15

sequencing diagnosis

Answer 15

resistance testing
surveillance
metagenomics
research

Question 16

PCR importance

Answer 16

amplification (sensitivity)
reverse transcriptase step may be required (if RNA virus)
primers (specificity)
DNA binding fluorescent dyes allow detection and quantification Qpcr by light sensors

Question 17

primers-

Answer 17

short single strand dna designed to match specific dna sequences of pathogens

Question 18

pathogen sequencing

Answer 18

allows order and identitiy of specific genetic
sequence
next generation sequencing- sequencing large amounts of genetic material at once
advantages- cheaper, faster, deeper
disadvanatge- not cheap, analysis, maintenance, still depends on specific primers
depth- pathogen sequencing- number of times is sequenced= confidence

Question 19

whole genome sequencing

Answer 19

• order and therefore identity of entire genetic sequence of an organism