Evolution and Emergence of New Viruses

Question 1

why do viruses evolve fast?

Answer 1

fast replication, replicate in large numbers, high mutation rate

Question 2

what is a quasispecies?

Answer 2

within a single infected person there will be virus genomes that a slightly different as they evolve whilst in the host

Question 3

what happens when bottlenecks arise?

Answer 3

only one or two quasispecies genomes will make it through

Question 4

how is drug resistance prevented?

Answer 4

drugs target different parts of virus life cycle so combination of antivirals used

Question 5

how do antibodies exert selection pressure on viruses?

Answer 5

if infected person has sub neutralising level of antibody the the virus will replicate and only the fittest survive = ANTIGENIC DRIFT

Question 6

how do new viruses emerge?

Answer 6

zoonosis, genetic variation, increased exposure, new discoveries

Question 7

what are global influences on emerging infections?

Answer 7

environmental modification, world population, climate change, travel, farming practices (monoculture), immunosuppressed people, medical progressive’s

Question 8

what are arboviruses? give examples

Answer 8

viruses transmitted to humans by arthropods, many are flaviviruses and alphavirues (+ sense RNA)
e.g. yellow fever, dengue, west nile, chikingunya

Question 9

why is global warming a concern for arboviruses?

Answer 9

less mosquito control, bigger distribution of mosquitos, more stagnant water in cities

Question 10

what is the west nile virus vector and dead end host?

Answer 10

vector = culled tarsalis

dead end vector = horses and humans

Question 11

how does west nile virus cause disease?

Answer 11

goes to the brain

Question 12

how many dengue serotypes are there and how do these affect sickness?

Answer 12

4
first infection not that bad, if infected again with different serotype the antibodies from 1st infection make you more sick = ANTIBODY DEPENDENT ENHANCEMENT OF INFECTION

Question 13

what are risk factors for dengue?

Answer 13

pre existing dengue antibodies, virus strain, age, secondary infections increase risk

Question 14

how do incorrect serotype dengue antibodies enhance infection?

Answer 14

gives viruses another way to get into cell as antibodies only bind loosely and don’t block the virus
antibodies then bind to Fc receptor on immune cells and carry virus into cells

Question 15

define zoonosis

Answer 15

disease which can be transmitted from animals to humans

Question 16

Name some zoonoses that don’t transmit efficiently and what this means?

Answer 16

SARS, ebola, hendra, nipah

can’t start pandemic

Question 17

give some characteristic about the SARS infection

Answer 17

nebulisers brought up virus from deep in lungs
high elderly mortality
patients only contagious late in infection so can isolate before spread
coronavirus = + sense RNA
from bats, racoons
spike protein is highly plastic

Question 18

what does multiple viral recombination allow?

Answer 18

new virus with new properties

antigenic shift

Question 19

what is MERS? what receptor does it use?

Answer 19

coronavirus, originate in bats/camels

DPP4 receptor

Question 20

what could be the next pandemic?

Answer 20

MERS, H7N9