evolution and emergence of new viruses Flashcards Preview

MCD - Microbiology > evolution and emergence of new viruses > Flashcards

Flashcards in evolution and emergence of new viruses Deck (19)
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1
Q

why do viruses evolve fast?

A
  • replicate fast
  • replicate in high numbers
  • high mutation rate
2
Q

what happens when a bottle neck happens?

A
  • only one or two of the genomes will make it through
3
Q

how to prevent drug resistance in HIV drugs?

A
  • must give a combination of antiviral drugs because that means that more simultaneous mutations are needed
  • this is unlikely
  • Error rate is roughly 1 per 10,000 nucleotides and as each genome is roughly
    10,000 nucleotides long,

therefore multiple drugs are needed

4
Q

how do antibodies also exert selection pressure on viruses ?

A
  • if the person has enough antibodies to kill the virus then they are fine
  • if the person only has enough antibodies to neutralise the amount of antibody the virus will replicate but only the fittest will survive
  • this is called antigenic drift
  • shown in influenza
5
Q

how might new viruses emerge?

A
  • zoonosis
  • genetic variation
  • increased exposure
  • new discoveries
6
Q

what are arboviruses?

A
  • A class of viruses transmitted to humans by arthropods such as mosquitoes and ticks.
7
Q

what are examples of arboviruses?

A
  • yellow fever
  • dengue
  • west nile
  • Chikingunya
8
Q

what are flaviviruses?

A
  • single strand positive-sense RNA genomes
9
Q

what is west nile virus?

A
  • belongs to a japanese group of flaviviruses

- it causes disease by going to the brain

10
Q

how do the effects of dengue fever change?

A
  • first time you get it you are not very sick
  • second time with the disease you are infected by a new serotype
  • the antibodies from before make you more sick
  • This is called Antibody Dependent Enhancement of the Infection
11
Q

what are risk factors for dengue fever?

A
  • Pre-existing anti-dengue antibody
  • virus strain
  • age
  • higher risk in secondary infection
12
Q

what happens if the dengue virus binds to homologous antibodies?

A
  • these antibodies are a perfect match to the virus
  • the viral antigens will bind the antibodies TIGHTLY and stop it from entering the cell

-

13
Q

what happens if the dengue virus binds to non homologous antibodies?

A
  • If infected by a different viral serotype - the antibodies bind loosely to the antigens but don’t block it
  • antibodies can bind to Fc receptors on immune cells
  • virus is carried to the immune cells
  • this leads to a cytokine storm and dengue haemorrhagic fever
14
Q

how is SARS transmitted?

A
  • respiratory droplets
15
Q

how does SARs affect people ?

A
  • elderly people show high mortality
  • Patients did not become contagious until quite late into the infection once
    they had become symptomatic
  • this means you can see who has SARs and isolate them
16
Q

what is a coranovirus?

A
  • positive-sense RNA genome
17
Q

what are the SARS coronoviruses?

A
Mammalian = Groups 1 + 2
Avian = Group 3
18
Q

what is MERS

A

Coronavirus

- uses zoonosis

19
Q

what does antigenic drift do?

A
  • it causes the virus to completely change
  • Humans live long enough to be re-infected so their antibodies can drive
    evolution