evolution and emergence of new viruses Flashcards
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
