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422 Virology > lecture 3- epidemiology of viral infections > Flashcards

lecture 3- epidemiology of viral infections Flashcards

1
Q

what is virus transmission?

A

passing of an infectious virus from an infected host to a susceptible host, regardless of whether the individual was previously infected

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2
Q

what is horizontal transmission

A

viral transmission between animals within the population at risk

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3
Q

is horizontal transmission direct or indirect?

A

both

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4
Q

when does vertical transmission occur?

A

in utero
during birth
colostrum
milk (first few weeks)

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5
Q

example of vertical transmission that can occur before birth (3)

A

BVDV, blue tongue, feline parvo

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6
Q

example of vertical transmission that can occur during birth

A

canine herpes virus

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7
Q

example of vertical transmission that can occur after birth

A

CAE, meadi-visna

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8
Q

consequences of vertical viral transmission

A

embryonic death/abortion, congenital disease, congenital defects

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9
Q

what are the 6 modes of transmission of horizontal viruses?

A

direct contact
indirect contact
common vehicles
airborne
vector-borne
iatrogenic

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10
Q

examples of direct contact

A

licking
rubbing
biting
sexual contact
skin abrasions

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11
Q

disease whose transmission is through biting? what mode of transport?

A

rabies, direct

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12
Q

disease whose transmission is through sexual contact?

A

herpes virus, direct

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13
Q

disease whose transmission is through skin abrasions?

A

papilloma virus, direct

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14
Q

examples of indirect contact

A

fomites (shared eating containers, beddings, restraint devices, vehicles, clothing, improperly sterilized surgical equipment)

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15
Q

examples of common vehicles

A
  • colostrum and milk
  • virus contaminated meat
  • virus contaminated bone products
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16
Q

diseases whose transmission is through colostrum/milk? what mode of transport?

A

caprine arthritis encephalitis virus (CAE), tick borne encephalitis virus

common vehicles

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17
Q

diseases whose transmission is through virus contaminated meat? what mode of transport?

A

classical swine fever, vesicular exanthema of swine

common vehicles

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18
Q

diseases whose transmission is through contaminated bone products? what mode of transport?

A

bovine spongiform encephalopathy (BSE)

common vehicles

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19
Q

examples of airborne modes of transport?

A

droplets, aerospols

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20
Q

large airborne droplets…

A

settle quickly

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21
Q

microdroplets either…

A

travel about a meter then evaporate

or

form droplet nucleus then become aerosols and remain suspended in the air for longer periods of time

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22
Q

examples of airborne diseases/their transmission (2 to note- 1 from cough/sneeze and 1 from dust/dander)

A

cough/sneeze –> influenza

dust/dander –> Marek’s disease virus

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23
Q

what are arboviruses?

A

arthropod borne

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24
Q

diseases whose transmission is through mosquitos? what mode of transport?

A

equine encephalitis

arboviruses

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25
Q

diseases whose transmission is through soft ticks? what mode of transport?

A

african swine fever virus

arbovirus

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26
Q

diseases whose transmission is through culicoides? what mode of transport?

A

blue tongue virus

arbovirus

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27
Q

what is iatrogenic transmission?

A

caused by doctor/animal handler

28
Q

2 examples of iatrogenic diseases?

A

equine infectious anemia
bovine leukemia virus

29
Q

what is nosocomial transmission?

A

acquired from clinics / hospitals

30
Q

the 1980 epidemic of canine parvovirus infection was caused by what mode of transmission?

A

nosocomial

31
Q

feline respiratory infections (calici virus infections) is caused by what mode of transmission?

A

nosocomial

32
Q

the 1976/1995 ebola epidemic in Zaire was caused by what mode of transmission?

A

nosocomial

33
Q

what are the mechanisms of survival of viruses in nature?

A
  1. physical stability/ environment
  2. maintenance of serial infections- chain of transmission within *animal *
    3.
34
Q

what is the relative stability of viruses transmitted by respiratory route?

A

low stability

35
Q

what is the relative stability of viruses transmitted by fecal-oral route?

A

higher stability

36
Q

enveloped viruses are generally…. what are the exceptions?

A

generally labile

exceptions are orf virus and Marek’s disease virus

37
Q

non enveloped viruses are generally …

A

stable

38
Q

example of non-enveloped viruses

A

adenoviruses, circoviruses

39
Q

what type of infection (clinical or subclinical) has a more productive source of virus?

A

clinical infection

40
Q

what type of infection (clinical or subclinical) has more numerous and more important/better opportunity for virus dissemination

A

subclinical

41
Q

why are subclinical infections significant? Explain in regards to BVDV

A

if a cow is persistently infected with BVDV (is subclinical) then they are still shedding the virus, despite looking healthy

42
Q

how to viruses maintain serial transmission? (3 patterns)

A
  1. acute self limiting
  2. persistent infection
  3. vector maintenance
43
Q

acute self limiting transmissions are affected by…

A

population size

44
Q

which serial transmission pattern is described by the following:
- infectious virus disappears with clinical recovery
- high yield of virus during disease
- continuous supply of susceptible hosts recquired

A

acute self limiting infection (hit and run strat)

45
Q

what are 3 viral examples of acute self limiting infection?

A

influenza
rota viral diarrhea
infectious bursal disease

46
Q

what are the three major types of persistent infection patterns?

A
  1. persistant infection
  2. chronic infection
  3. latent infection
47
Q

which serial transmission pattern is described by the following:
- clinical disease and death with result after years of shedding the virus with subclinical infection

A

persistent infection (with persistent pattern)

48
Q

what disease example shows a persistent infection with persistent pattern?

A

BVDV
congenital infection

49
Q

which serial transmission pattern is described by the following:
- clinical disease and high yield of infectious virus initially resembles acute infection
- clinical recovery follows shedding of a virus at low levels for years

A

chronic infection (persistent pattern)

50
Q

what are 2 disease examples that show chronic infection (persistent pattern)?

A

FMDV (foot and mouth)
feline calici virus

51
Q

which serial transmission pattern is described by the following:
- intermediate shedding with/without clinical consequences

A

latent infection (persistent pattern)

52
Q

during latent periods of latent infection, are viral particles being shed?

A

no

53
Q

what is a viral example of latent infection (persistent pattern)?

A

herpesvirus

54
Q

where does BHV-1 replication occur?

A

nasal mucosa

55
Q

in BHV-1, where is life long latency established?

A
  • trigeminal ganglia-neurons
  • tonsillar lymphoid follicles- T cells
56
Q

what triggers BHV-1 to reactivate? where does productive infection occur?

A

triggered during stress or when immunity is low

establishes productive infection in primary replication sites (trachea and nasal mucosa)

57
Q

what 3 factors influence the prevalence of emerging viral diseases?

A

1) host determinants
2) constant changes in environment
3) viral determinants

58
Q

how does the evolution of viruses occur via milder genetic changes?

A

viral replication –> mutations –> antigenic drift

59
Q

which have a higher mutation rate, RNA or DNA viruses? why?

A

RNA viruses lack proofreading since most replicate in the cytoplasm, therefore they have a higher mutation rate than DNA

60
Q

how does the evolution of viruses occur via drastic genetic changes? 2 ways

A

1) template switching between closely related viruses
2) exchange of entire gene segments (rearrangement)

61
Q

how does template switching between closely related viruses occur?

A

co-infection of a cell by genetically distinct viruses can lead to the generation of recombinant viruses

62
Q

what is an example of template switching

A

ancient sinbis like viruses + eastern equine encephalitis virus = western equine encephalitis cirus

63
Q

how does exchange of entire gene segments (reassortment) to create a new virus occur?

A

co-infection of a cell by genetically distinct strains of a segmented virus can generate different combinations of reassortment progeny

64
Q

examples of viruses created by reassortment? 4

A

-arena and birna viruses (2 segments)
- bunyaviridae (3 segments)
-orthomyxoviridae (6-8 segments)
-reoviridae (12 segments)

65
Q

what kind of receptors are associated with influenza virus

A

sialic acid

422 Virology (15 decks)

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