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Virology Lectures > Zoonoses and emerging human viral infections > Flashcards

Zoonoses and emerging human viral infections Flashcards

1
Q

Definition of an emerging disease

A

A new disease of humans, not previously seen or a recurrence of an infection that has previously disappeared from the human population

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2
Q

Definition of enzootic

A

infection maintained in an animal population

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3
Q

Definition of epizootic

A

increased transmission of infection in an animal population

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4
Q

Why are viruses host specific?

A
  • few genes

- entirely dependent on host cell for replicaton

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5
Q

Adaptive mechanisms of zoonotic viruses

A
  • point mutation
  • recombination
  • reassortment
  • host RNA modification
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6
Q

Define a quasi-species

A

A population of related viruses that differ by point mutations

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7
Q

Possible effects of point mutations

A

Altered protein structure

  • altered antigenicity
  • altered drug senstivity
  • altered function

Non-coding region
- altered level of expression

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8
Q

Describe the Poliovirus and tissue tropism

A
  • Enterovirus that replicates in GALT
  • change in tissue tropism triggered by favourable mutation
  • replicate in CNS
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9
Q

Examples of viruses that often use recombination

A
  • coronaviruses
  • picornaviruses
  • retroviruses
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10
Q

Examples of viruses that often use reassortment

A
  • Influenza A
  • rotaviruses
  • bunyaviridae
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11
Q

Another name for virus reassortment

A

Antigenic shift

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12
Q

Characteristics of fulminant clinical illness

A
  • fever and rash
  • encephalitis
  • viral haemorrhagic fever
  • shock syndrome
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13
Q

Pathogenesis of Rabies

A

Enters nerve endings by binding acetyl choline receptors

Travels up axons to the brain

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14
Q

Reservoir hosts of Rabies

A
  • carnivora

- chiroptera (bats)

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15
Q

Describe Marburg and Ebolavirus disease

A
  • Haemorrhagic fever
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16
Q

Contributing factors for Ebola outbreaks

A
  • poverty
  • destroyed infrastructure
  • no trust in authority
  • delayed recognition of outbreak
  • collapsed healthcare system
  • slow international response
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17
Q

Incubation period of Ebola

A

2-21 day

18
Q

Treatment of Ebola

A
  • replace lost fluid

- maintain BP

19
Q

What is a spill over host?

A

A second animal host that is not the usual reservoir

20
Q

Problems with spill over hosts

A
  • amplify infection
  • often get ill
  • contact with humans
21
Q

Types of arthropod vectors

A
  • mosquitoes
  • ticks
  • sandflies
22
Q

Most common VHF in SA

A

Crimean Congo Haemorrhagic fever

23
Q

Vector of Congo fever

A

tick

24
Q

Yellow fever virus type

A

Flavivirus

25
Q

Animal reservoir of YF

A

forest monkey

26
Q

Vector of YF

A

various species of Aedes and Haemogogus mosquitoes

27
Q

Vector of Dengue fever

A

Aedes Aegypti mosquito

28
Q

Predominant cycle of dengue fever

A

Urban

29
Q

Steps to becoming a human infection

A
  • exposure to reservoir
  • cross species infection
  • transmission to a 2nd human host
  • adaptation to a new species
  • sustained human to human transmission
30
Q

Staged of an animal virus

A
  • agent only in animals
  • primary infection
  • limited outbreak
  • long outbreak
  • exclusive human agent
31
Q

Factors which determine the ability of an organism to establish itself as a human infection

A
  • duration of infectivity
  • ease of transmission to new hosts
  • milder disease phenotype
  • capacity for immune evasion
  • population size/density
32
Q

Define a reproduction rate

A

The average number of secondary cases generated by a single infected individual

33
Q

Define herd immunity

A

Collective immunity to a pathogen in the population

34
Q

Phases of global alert in pandemic monitoring

A 
1 - animal infection
2 - potential pandemic threat
3 - sporadic human cases
4 - significant increase in risk of pandemic
5 - pandemic is imminent
6 - pandemic phase
35
Q

Virology of influenza virus

A

Orthomyxovirus
Segmented genome
2 envelope glycoproteins

36
Q

Why is influenza so antigenically variable?

A
  • Immunity is directed to HA

- high mutation rate of this region

37
Q

How does a flu pandemic arise?

A
  • new strains of influenza arise from reassortment between human and avain flu strains
38
Q

Human factors responsible for emerging infections

A
  • population growth
  • urbanisation
  • population movement
  • global air travel
  • food production
39
Q

Viral factors responsible for emerging infections

A
  • new vector
  • new vertebrate hosts
  • antigenic variation
  • altered pathogenicity
  • altered tissue tropism
40
Q

Ecological factors responsible for emerging infections

A
  • altered prevalence of animal species
  • proliferation of vectors
  • expansion of vectors to new areas

Virology Lectures (13 decks)

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