7 - Evolution and emergence of new viruses Flashcards Preview

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Flashcards in 7 - Evolution and emergence of new viruses Deck (16):

What is meant by quasi species?

within a single infected person, they will have viral genomes that are slightly different because they evolve whilst they are in the host


How can drug resistance be prevented?

use a combination of antiviral drugs


What does HAART stand for?

Highly Active Anti-Retroviral Therapy


What is antigenic drift?

when antigens gradually change over a period of time due to pressure exerted by antibodies


How do new viruses emerge?

- zoonosis
- genetic variation
- increased exposure - travel or world population
- increased exposure - spread of vector
- new discoveries


Define arboviruses

a class of viruses transmitted to humans by arthropods such as mosquitoes and ticks


Give some examples of arboviruses

yellow fever
west nile

NOTE: many of these are flaviviruses


What are flaviviruses?

have single stranded positive-sense RNA genomes


What is meant by Antibody Dependent Enhancement of the Infection with reference to dengue fever?

4 serotypes of the dengue virus
- the first time you get dengue, you are ill, but not severely
- the second time, you will be infected with a different serotype - and the antibodies that you develop the first time will make you more ill


What is meant by host range?

refers to an organism's ability to infect and reproduce in wide range of organisms.

The spectrum of strains of bacterial species that a given strain of phage can infect. The range of cells that can act as a host to a virus or bacteriophage.


Dengue antibodies can neutralise or. enhance infections. What is the mechanism by which they enhance it?

- the virus binds to the wrong anti-dengue antibodies, and this gives it another way of getting into cells
- dengue virus usually gets into the cells by binding to specific receptors
- if you have homogenous antibodies (all the same), viral antigens will bind them tightly and stop it from entering the cell
- if infected by a different viral serotype, the antibodies will bind the antigens loosely but won't block it
- then the antibodies will bind to Fc receptors on immune cells, thus carrying the virus into immune cells
- this leads to a cytokine storm and dengue haemorrhagic fever


What is meant by zoonosis?

a disease that can be transmitted from animals to humans
(more specifically, a disease that normally exists in animals but that can infect humans)


Which zoonoses have the potential to start a pandemic but do not transmit efficiently?



What does SARS stand for?
How it is transmitted?

Severe Acute Respiratory Syndrome
transmitted via respiratory droplets


What is the time relationship between becoming symptomatic and contagious of SARS?

does not become contagious until late into infection once it has become symptomatic
therefore, the virus is containable

NOTE: flu is the opposite


Swine flu and antigenic drift

- as the virus circulated in humans, it changed gradually and so it has antigenic subtypes
- you do not get antigenic drift in pigs because they do not live long enough to be re-infected
- humans live long enough to be re-infected so their antibodies drive evolution of the virus
- Now, the H1 virus in totally different to that in humans