17. Diagnosis and Evolution of SARS-CoV2 Flashcards
what does PCR detect, has this been a useful tool?
detects part of the viral genome
proven not to be capable of handling diagnosis at population level (overwhelmed labs)
what are some clinical symptoms of SARS-CoV2
fever, fatigue, cough, shortness of breath, sneezing
what has been a good alternative to PCR testing
rapid antigen tests (lateral flows)
evaluate lateral flow tests
perks:
- easy to use
- does not require labs
- easy to dispense
- quick results
cons:
- only available in western countries
- false negatives (low specificity)
describe the Ellis & Delbruck experiment
- grow bacteriophages in E.coli
- proved phages develop intracellularly
describe the Hershey & Chase experiment
showed that only the DNA of a virus needs to enter a bacterium to infect it
describe Fraenkel et al
showed that RNA is the genetic material of tobacco mosaic virus
how can we quantify viruses
with plaque forming units
what does PFU show?
an indication of cells that have died because of viral infection
- allows us to quantify the presence of a virus
what does haemagglutinin do?
bind to the surface of cells forming cross links = cause cells to clump together (agglutinate)
how do you perform a haemagluttination assay
dilute virus in wells and add the RBCs - where there is virus present, clumping will occur
how does a haemagglutination inhibition assay work?
same protocol as haemagluttinin assay, but add antiviral to the mix
is there is no aggulutination = virus is not present
what does sandwich ELISA assay test for
the presence of viral antigens
how does sandwich ELISA work
add sample to wells, if virus present it will bind to stationary antibodies
then add a further antibody which has a conjoined enzyme
if virus is present, any substrates added to the sample will be converted into a colourful compound by the enzyme, this colourful compound can be quantified using a spectrophotometer
how does antibody-capture ELISA work
wells coated with virus antigen, test samples (potentially containing antibody) are added to the wells
samples washed away, any remaining bound antibody can be detected using secondary antibody
what does ELISA antibody-capture test for
the presence of antibodies
how does neutralisation assay work
tests whether antibodies in the sample bind well enough to the virus to deactivate it
quantifies the presence of functional antibodies to the virus
by what 3 ways do viruses evolve
point mutations
recombination
assortment
what virus has a high mutation rate, why?
influenza
assortment occurs frequently
what virus has a low mutation ate
SARS-CoV2
- no segmented genome so no assortment
what is the difference between the latent and incubation period
latent period = time interval between contracting the disease and becoming infectious
incubation period = time interval between contracting the disease and showing symptoms
what is the average latent period for COVID-19
5.6 days
