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BIO220 > BIO220 Lecture 9 > Flashcards

BIO220 Lecture 9 Flashcards

Virulence II - Evolution of virulence - Evolution of influenza - Polio

1
Q

3 stages of virulence evolution

A
  1. Accidental infection
  2. Virulence evolution soon after invasion
  3. Evolution of optimal virulence
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2
Q

Accidental infection

A

Pathogens cross species boundaries
Mostly low virulent.
This rarely happens.

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3
Q

How might pathogens infect novel hosts?

A
  • Infect one, but secondary infections won’t happen

- Short-lived, high virulence infection that dies quickly

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4
Q

Why might accidental infections be very virulent?

A

Cross species, so new host as no immune defence against novel pathogen

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5
Q

Secondary infections

A

Infection from host to host

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6
Q

What does successful invasion require?

A

Chain of host to host transmissions

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7
Q

Epidemic

A

Rapid increase in number of infected hosts

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8
Q

What happens during stage two of virulence evolution

A

Epidemic happens
Rapid evolution of pathogen and virulence
Many hosts infected

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9
Q

What happens during stage 3 of virulence evolution

A

Reach trade-off boundary between high & low virulence.
Evolution of pathogen slows, adaptation occurs.
Transmission frequency is optimized.

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10
Q

Problem with confirming death due to flu

A

Death is usually doe to associated illnesses, so difficult to confirm if flu was actually the cause.

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11
Q

Once you get one strain of the flu…

A

You are immune to that strain for life

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12
Q

HA

A

Hemagglutinin protein

Surface protein that allow virus to bind to target cell

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13
Q

NA

A

Surface protein that allow virus to escape from host cell and infect other cells

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14
Q

Seasonal flu caused by

A

Influenza A

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15
Q

Pandemics are caused by…

A

Influenza A

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16
Q

Influenza A evolves…

A

very fast

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17
Q

Rapid evolution of the flu occurs at what sites on the virus?

A

HA and NA sites (recognized by the immune system)

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18
Q

Descendent of recent flu strains?

A

From single ancestor

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19
Q

What happens at antigenic sites on HA?

A

Continuous nucleotide substitutions

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20
Q

Where does mutations occur on HA and NA?

A

Antigenic sites

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21
Q

___ plays a strong role in determining influenza evolution

A

Human immune system

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22
Q

What do we use to make vaccines?

A

The most successful strain of the current year (most number of mutations)

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23
Q

How are vaccines tested?

A

When new strains of the virus appear, they are tested against current vaccines. If it does not work new vaccines must be made.

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24
Q

How long does it take to make a vaccine?

A

6 months

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25
Q

How are vaccines made?

A

Inactivated viruses cultured in eggs

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26
Q

How are viruses used for vaccines inactivated?

A

Damage nucleic acid by chemicals or radiation

27
Q

What type of vaccine is used?

A

Trivalent vaccine:

  • 2 influenza A strains - H1N1, H3N2
  • 1 influenza B strain
28
Q

Main point of getting a vaccine

A

Stop transmission to OTHER people

29
Q

3 types of the flu

A
  1. Seasonal flu
  2. Pandemic flu
  3. Avian flu
30
Q

Seasonal flu

A

respiratory illness transmitted host-to-host. Immunity and vaccine available

31
Q

Pandemic flu

A

Global outbreak of a flu transmitted from host to host. No immunity.

32
Q

Pandemic flus

A
  1. 1918 Spanish flu
  2. 1957 Asian flu
  3. 1968 Hong Kong flu
33
Q

Avian flu

A

H5N1 virus found in birds:
deadly to domestic fowl and humans. No secondary infections.
No immunity, no vaccines.

34
Q

Antigenic drift

A

Accumulation of many small mutations

35
Q

Antigenic shift

A

Reassortment of RNA segments from different strains = gene flow

36
Q

The Spanish Flu was due to…

A

antigenic drift; an avian strain that was able to secondary infect

37
Q

Most influenza A viruses are descendent of…

A

1918 H1N1

38
Q

The H1N1 occurred in ___ waves, and ___ happened between waves.

A

3

Drift

39
Q

Who was most affected by the 1918 H1N1?

A

Young, old, middle age

W shaped graph

40
Q

Who is usually most affected by the flu?

A

Young and old people (U shaped graph)

41
Q

1918 H1N1 also appeared in what species?

A

Pigs

42
Q

What made up the 2009 H1N1 virus?

A

3 pig viruses, avian, human viruses

-> antigenic shift

43
Q

the 2009 H1N1 hit in ___ waves

A

2

44
Q

2009 H1N1 originated in…

A

Mexico

45
Q

Avian flu first appeared in…

A

Hong Kong

46
Q

Poliomyetlitis

A

Virus that causes poliomyelitis

47
Q

How do we get polio?

A

through the mouth

48
Q

Where does poliomyelitis replicate?

A

GI tract

49
Q

How is polio transmitted?

A

In feces

50
Q

Where does poliomyelitis affect?

A

GI tract, bloodstream, CNS

51
Q

what happens if the CNS is affected by polio?

A

Partial paralysis, maybe death

52
Q

IPV

A

Inactivated Polio Vaccine

53
Q

What is IPV inactivated with?

A

Formaldehyde

54
Q

How is IPV administered?

A

syringe

55
Q

OPV

A

Oral Polio Vaccine

56
Q

How was OPV made?

A

Selected for low virulence strains of polio in monkey kidneys. These live, non-virulent strains was used for vaccination.

57
Q

What are 2 advantages of OPV?

A
  1. No needles needed

2. Vaccinated individual can vaccinate others

58
Q

VAPP

A

Vaccine Associated Paralytic Polio

59
Q

What caused VAPP?

A

Back mutations of OPV

60
Q

What is VAPP?

A

After successful vaccinations, there were still some polio outbreaks (not completely gone). These outbreaks were due to VAPP.

61
Q

Sequential vaccination

A

IPV first, then OPV

Combination increases effectiveness, and IPV will prevent back mutations of OPV

62
Q

Where did the polio outbreak in 2000 happen?

A

Haiti

63
Q

Why did the polio outbreak in 2000 happen?

A

OPV back mutation

BIO220 (24 decks)

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