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Emerging viruses Flashcards

1
Q

Rhinovirus C has been around for?

A

~8000 years

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2
Q

When did we learn about rhinovirus C?

A

2006

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3
Q

Why did it take so long for us to identify rhinovirus C?

A

Could not propagate it in cell culture

Did not know it required the CDHR3 cadherin receptor

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4
Q

Newly emerging viruses are better known as?

A

Newly detected viruses

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5
Q

What will increase the number of newly detected viruses?

A

Improvements in technology and diagnosis

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6
Q

How can newly evolved viruses emerge?

A

Through mutation

Through recombination and reassortment

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7
Q

Why is a one health approach important?

A

As 6/10 of infectious diseases in humans are spread by animals. There is a holism, the health of humans and animals is interconnected

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8
Q

What is required for a newly emerged zoonotic virus?

A

Species jump

Needs to overcome the host range barrier

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9
Q

Why is pandemic influenza relatively infrequently?

A

Due to the host range barrier

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10
Q

What is the host range barrier?

A

The barrier which must be overcome to allow transmission in other species

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11
Q

The strength of the host range barrier determines?

A

The strength of the host range barrier determines the likelihood that the virus will spread from the host species to a new host species

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12
Q

Why do viruses emerge?

A
  • Human activity
  • Economic situation
  • Health of the country- malnutrition
  • Changes in farming practices
  • Changes in land use
  • Ecological changes: Introduction of a new species, loss of a predator, increased geographical range
  • Climate change
  • International travel
  • International trade
  • Failure of public health programmes
  • Contamination of water/food supplies
  • Invasion
  • Pathogen evolution
  • Changes in human/societal demographics
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13
Q

What limits emerging viruses?

A
  • Receptor specificity
  • Tropism
  • Host range barrier
  • Natural immunity
  • Cross protection e.g. cowpox can protect from smallpox. The pox viruses are morphologically indistinguishable but are immunologically similar which allows cross protection
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14
Q

Why are emerging viruses so virulent?

A
  • No co-evolution with the new host. There is often an imbalance between the viral immunomodulators and host effectors
  • Host population is immunologically naive
  • There is no active attenuation of the virus. As the virus exists in a reservoir population it does not rely on human-to-human transmission. It does not need to become less virulent to facilitate its transmission as it can ‘spillover’ into human populations. Survival of the virus is not dependent on transmission between humans.
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15
Q

What is pathogenesis?

A

Qualitative description of disease. It is mechanism by which the virus causes disease. The process by which disease is caused

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16
Q

What is virulence?

A

It is quantitative, it is non-scalar and relative. It is the extent of disease caused

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17
Q

How can virulence be measured?

A
  • Fever, the temperature caused
  • Weightloss
  • Mortality
  • Morbidity
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18
Q

Why is virulence important to study?

A

The more we know the more we can predict the virulence of emerging diseases

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19
Q

How does direct transmission impact virulence?

A

Leads to decreased virulence

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20
Q

Why does direct transmission lead to decreased virulence?

A

Due to the transmission-mortality tradeoff

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21
Q

How does environmental transmission impact virulence?

A

Waterborne transmission is associated with increased virulence
Sit and wait transmission is associated with increased virulence

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22
Q

Environmental transmission does not rely on?

A

Host motility

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23
Q

Example of a bacteria which relies on sit and wait transmission?

A

Anthrax

Bacillus anthracis

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24
Q

Anthrax is caused by?

A

Bacillus anthracis

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25
Example of a highly virulent bacteria spread by water?
Cholera
26
How does vectored transmission impact virulence?
Associated with increased virulence
27
How does vertical transmission impact virulence?
Associated with decreased virulence
28
Virus example spread by direct transmission?
1950s myxoma virus released in Southern Australia Had an initial fatality rate of 99% Fatality rate reduced to 50% Eventually the rabbit population recovered
29
Virus example spread by vector transmission?
Rabbit haemorrhagic virus
30
Rabbit haemorrhagic virus is spread by?
Blowflies
31
Which disease became more virulent due to imperfect vaccination?
Marek's disease
32
What is perfect vaccination?
Perfect vaccination prevents an individual becoming infected and spreading the disease
33
What is imperfect vaccination?
This reduces the symptoms of disease and mortality associated; however, the vaccinated individuals can still transmit the virus
34
Why was imperfect vaccination associated with higher virulence?
The vaccinated individuals could transmit the virus to non-vaccinated individuals. They would shed virus for prolonged periods and would transmit the virus. Meant that the virus did not have a selection to become less virulent
35
HIV-1 is thought to have arisen from?
Chimpanzees
36
HIV-2 is thought to have arisen from?
Sooty mangabeys
37
HIV-1 evolved from?
SIV
38
SIV?
Simian Immunodeficiency virus
39
How many independent events of SIV emerging to form HIV?
3 emergence events
40
The three separate SIV emergence events created?
The three separate emergence events resulted in HIV-1 groups of M,N and O
41
How did SIV originally infect humans?
Via the bushmeat trade, direct blood-to-blood contact
42
What may be causing HIV to evolve to become less virulent, what is the selection pressure?
Direct sexual transmission Drugs- anti-HIV drugs are given to people who show symptoms of HIV. The drugs reduce the viral blood titre to undetectable levels such that the virus can no longer be transmitted. Therefore, more virulent HIV is detected sooner and will not be spread due to drug administration. Therefore, the less virulent types of HIV will spread more frequently and may result in a reduced virulence of HIV overall.
43
H7N9 was first seen where and when?
China | 2013
44
When did H7N9 evolve to become HPAI?
February 2017 is when this was first noticed
45
Why is H7N9 a threat?
- PB2 E627-->K627 mutation is rapidly selected for during human infection - Dual receptor binding specificity - Multibasic cleavage site
46
What was China's response in 2017?
Began vaccinating chickens against H7N9
47
MERS was first identified where?
Saudi Arabia
48
When was MERS first identified?
2012
49
MERS reservoir?
Dromedary camels
50
Hendra virus history?
First seen in 1994, infected 21 racehorses and a trainer
51
Hendra virus was first observed in?
1994
52
Hendra virus reservoir?
Pteropus bats
53
Nipah reservoir?
Pteropus bats
54
Potential drug treatment for hendra virus?
Ribavirin
55
Ribavirin?
Chain terminator | Guanosine analogue
56
Nipah virus outbreak first occurred in?
Malaysia
57
What caused the spread of Nipah?
Anthropogenic fires- slash and burn deforestation. This was exacerbated by the El Nino event which led to severe droughts and impacted fruiting
58
What was the novel route of Nipah transmission in Bangladesh?
Via palm date sap
59
SARS emerged in?
2003
60
When did the spread of SARS stop?
2004
61
Where did SARS emerge?
China
62
SARS reservoir?
Cave dwelling horse shoe bats
63
When was the most recent Ebola outbreak?
2014
64
Where did the most recent Ebola outbreak occur?
West Africa
65
Countries impacted by the 2014 Ebola outbreak?
Sierra Leone, Liberia, Guinea
66
Why was West Africa impacted more?
- Lack of infrastructure, poor road connections, telecommunication services - Perception of hospitals - Reliance on traditional healers - Shortage of trained public health workers - Cultural and behavioural practices: An estimated 80% of cases in Sierra Leone were believed to be due to cultural practices including the washing and burial of bodies - Political instability, many of the affected countries had recently emerged from years of civil war and political unrest... cohort of uneducated adults as a consequence
67
Why are Ebola outbreaks not as bad in central Africa?
- Have occurred here previously - They know how to recognise the signs of an outbreak - They have better healthcare and precautions in place - WHO monitoring - Trained staff
68
West Nile Virus is transmitted by?
Mosquitos
69
West Nile Virus spread globally through?
Bird migration
70
Blue tongue disease impacts?
Sheep
71
Blue tongue disease is spread by?
Midges
72
Blue tongue disease is caused by?
A virus
73
How is the geographical range of blue tongue disease increasing?
Due to climate change, has allowed the range of midges to increase. Species/vector jump of the virus to a different midge species was then able to occur
74
Zika virus outbreak occurred in?
2015
75
Zika virus causes?
Microcephaly
76
What is microcephaly?
Deformation of the head, smaller head
77
Zika virus is transmitted by which mosquito?
Aedes agypti
78
Emerging adenovirus?
HAdV-55
79
Which countries has HAdV-55 been observed in?
China, Spain, South Korea, Turkey, Singapore
80
HAdV-55 can lead to?
Severe pneumonia
81
HAdV-55 was first characterised where?
China
82
HAdV-55 was first characterised when?
2006
83
Most HAdV-55 outbreaks are?
Random and sporadic

MM- Viruses (13 decks)

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