ICL 1.1: Zoonotic Viruses I Flashcards

1
Q

what is an emerging virus?

A

it’s a causative agent of a new or previously unrecognized infection

this is NOT just a virus that we haven’t heard about that shows up somewhere, it could also be a virus that is showing up in a geographically new area

they are infections that have recently appeared within a population or those whose incidence or geographic range is rapidly increasing or threatens to increase in the near future

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2
Q

what could cause an emerging virus to come into existence?

A
  1. expanded host range
  2. transmission from wild/domesticated animals to humans (zoonosis)
  3. cross-species infection may establish new virus in the population
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3
Q

in what facilities are viruses studied?

A

special high containment laboratories are required to study viruses or test patient samples

this is what makes research so slow because you have to work in special containment labs so that the researchers are safe and the bug doesn’t escape which takes lots of time and money

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4
Q

which viruses are BSL-3?

A

BLS = biosafety level

  1. West Nile virus
  2. Chikungunya virus
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5
Q

which viruses are BSL-4?

A

Ebola

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6
Q

what are zoonoses?

A

infections that can be transmitted to humans from animals

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7
Q

what are the two main ways through which zooneses are transmitted?

A
  1. arthropods –> often through blood meals like with mosquitos
  2. vertebrates –> bites, body fluids, inhalation, etc.

zooneses = infections that can be transmitted to humans from animals

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8
Q

what is a host?

A

any species capable of sustained viral replication

so lots of things can be hosts!

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9
Q

what is a natural host/reservoir?

A

the host in the absence of human intervention

this is the host that you’d see in nature

often times, a virus has multiple reservoir hosts which makes getting rid of the virus tricky

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10
Q

what is a dead end host?

A

an accidental host that is not important in virus life cycle

the dead end host usually doesn’t further transmit the virus

humans are usually the dead end host! we aren’t part of the cycle; if we all died the virus would still exist and be able to replicate

however, we do usually get the most severe form of the disease

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11
Q

which viruses are arthropod transmitted viruses?

A
  1. Yellow fever virus (Flaviviridae)
  2. Dengue virus (Flaviviridae)
  3. West Nile virus (Flaviviridae)
  4. Powassan virus (Flaviviridae)
  5. St. Louis encephalitis virus (Flaviviridae)
  6. Eastern equine encephalitis virus (Togaviridae)
  7. Chikungunya virus (Togaviridae)
  8. La Crosse virus (Bunyaviridae)
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12
Q

which viruses are rodent transmitted viruses?

A
  1. Hantaviruses (Bunyaviridae)

2. Lassa virus and LCMV (Arenaviridae)

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13
Q

which viruses are bat associated viruses?

A
  1. Rabies virus (Rhabdoviridae)
  2. Ebola virus and Marburg virus (Filoviridae)
  3. Nipah and Hendra viruses (Paramyxoviridae)
  4. SARS (Coronaviridae)
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14
Q

which viruses have a severe association with hemorrhagic fever?

A
  1. Yellow fever virus (Flaviviridae)
  2. Dengue virus (Flaviviridae)
  3. Hanataviruses (Bunyaviridae)*
  4. Lassa virus and LCMV (Arenaviridae)
  5. Ebola virus and Marburg virus (Filoviridae)
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15
Q

which viruses have a severe association with encephalitis?

A
  1. West Nile virus (Flaviviridae)
  2. Powassan virus (Flaviviridae)*
  3. St. Louis encephalitis virus (Flaviviridae)
  4. Eastern equine encephalitis virus (Togaviridae)
  5. La Crosse virus (Bunyaviridae)
  6. Rabies virus (Rhabdoviridae)
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16
Q

which viruses have a severe association with respiratory problems?

A
  1. Nipah and Hendra viruses (Paramyxoviridae)

2. SARS (Coronaviridae)

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17
Q

which virus has a severe association with arthralgia?

A

Chikungunya virus (Togaviridae)

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18
Q

what are the severe disease associations of Dengue virus?

A
  1. hemorrhagic fever

2. arthralgia

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19
Q

what are the severe disease associations of Powassan virus?

A
  1. encephalitis

2. hemorrhagic fever

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20
Q

what are the severe disease associations of Hantaviruses?

A
  1. hemorrhagic fever

2. respiratory problems

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21
Q

what are the severe disease associations of the Nipah and Hendra viruses?

A
  1. respiratory problems

2. encephalitis

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22
Q

what is a vector?

A

an animal that delivers a virus

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23
Q

what are arboviruses?

A

arboviruses = arthropod-born viruses (blood sucking)

arbovirus is a collective term that groups together all the arthropod-borne viruses - it is NOT a virus family!!

there are hundreds of arboviruses

they all infect vertebrates

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24
Q

what is the sequence of transmission with arboviruses?

A

they are spread by ticks or mosquitos that have the virus

the tick/mosquito then transfers the virus to a vertebra such as humans, monkeys, pigs etc.

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25
Q

how do you control the spread of arboviruses?

A

best strategy for control is vector control

it’s hard to make a vaccine against the hundreds of different arboviruses so instead you have to do vector control and get rid of the mosquito or tick that’s transmitting all the viruses!

if you cut down on the vectors, you cut down on the risk of transmission!

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26
Q

which 4 virus families are arboviruses?

A
  1. togaviridae
  2. flaviviridae
  3. bunyaviridae
  4. reoviridae
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27
Q

what is the structure of the togaviridae virus family?

A

enveloped, icasahedral (+) sense ssRNA

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28
Q

what is the structure of the flaviviridae virus family?

A

enveloped, icasahedral (+) sense ssRNA

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29
Q

what is the structure of the bunyaviridae virus family?

A

enveloped, helical (-) sense, segmented ssRNA

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30
Q

what is the structure of the reoviridae virus family?

A

naked, icosahedral, segmented dsRNA

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31
Q

what are the common features of arboviral diseases?

A
  1. often subclinical
  2. initial replication in endothelial cells and macrophages/monocyte lineage
  3. viremia = virus in the blood
  4. low % infections lead to clinical cases
  5. not all clinical cases lead to major disease
  6. probably underdiagnosed
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32
Q

why are arboviral diseases probably underdiagnosed?

A

they’re usually subclinical so you won’t really develop symptoms and even if you do, it’ll just be a headache or muscle pain

so most people don’t go the hospital because they don’t have severe symptoms which means most viruses are probably under-diagnosed

this makes it really hard to assess how many people have actually been infected/exposed to the virus

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33
Q

what is viremia?

A

virus in the blood

you don’t always have high levels of viremia which makes it hard for the mosquito to pick up the virus from the blood and then transmit it to another animal

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34
Q

which cells are involved initially in arbovirus replication?

A

initial replication is in endothelial cells and macrophage/monocyte lineage

this is because these are the cells right at the bite site and the cells that are recruited to the site so they’re the first to get infected!

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35
Q

how do you diagnose arboviruses?

A
  1. ELISA
  2. antigen detection
  3. serum neutralization
  4. RT-PCR (because arboviruses are all RNA viruses)
  5. virus isolation by cell culture
36
Q

how do you treat West Nile virus?

A

supportive care

you just want to make sure they can breath so you keep them on a ventilator since we don’t have any antivirals to treat them with….

37
Q

how can you tell which geographical regions are at a higher risk for certain viruses?

A

pathogens are associated with some kind of vector so it’s easy to tell who’s at risk for these diseases based on where the vectors are commonly found

so if something is being transmitted by a tick, the areas more prone to get the disease being carried by this tick are the places that the tick lives!

so just keep this in mind when someone travels which viruses are common in those areas that they went to

38
Q

how do we prevent arboviruses?

A
  1. surveillance = screen animals for infection!
  2. vector control
  3. personal protection = repellent, clothing, activity avoidance
  4. vaccination (rarely)
39
Q

when would we vaccinate against arboviruses?

A

it’s very rare that we can vaccinate against arboviruses

usually when we can, they’re travel vaccines!

we don’t need these vaccines here in the US, but when people go other places they do need them

40
Q

which specific viruses are arboviruses associated with encephalitis in the USA?

A

FLAVIVIRIDAE
1. Powassan virus

  1. St. Louis encephalitis
  2. West Nile virus

BUNYAVIRIDAE
1. California serogroup: La Crosse virus & Jamestown Canyon

TOGAVIRIDAE
1. Eastern equine encephalitis virus (triple E!)

**they all have mosquito vectors except Powassan virus which is a tick vector

41
Q

what is the occurence, vector, reservoir and disease associated with Powassan virus?

A

disease = encephalitis

occurence = North America

vector = tick

reservoir = rodents

flaviviridae family = enveloped, icasahedral (+) sense ssRNA

42
Q

what is the occurence, vector, reservoir and disease associated with St. Louis encephalitis virus?

A

disease = encephalitis

occurence = North America, Eastern US

vector = mosquito

reservoir = birds

flaviviridae family = enveloped, icasahedral (+) sense ssRNA

43
Q

what is the occurence, vector, reservoir and disease associated with West Nile virus?

A

disease = encephalitis

occurrence = North America, Europe, Africa

vector = mosquito

reservoir = birds

flaviviridae family = enveloped, icasahedral (+) sense ssRNA

44
Q

what is the occurence, vector, reservoir and disease associated with La Cross and Jamestown Canyon viruses?

A

disease = encephalitis

occurence = North America

vector = mosquiot

reservoir = small mammales like chipmunks, squirrels, etc.

bunyaviridae family = enveloped, helical (-) sense, segmented ssRNA

45
Q

what is the occurence, vector, reservoir and disease associated with eastern equine encephalitis virus?

A

disease = encephalitis

occurence = eastern US, Canada

vector = mosquito

reservoir = birds

togaviridae family = enveloped, icasahedral (+) sense ssRNA

46
Q

what are serogroups?

A

when you have antibodies against a certain virus, sometimes the virus is close enough in structure that your antibodies against the first virus will partially recognize it if the surface glycoproteins of both viruses are similar enough

this would mean that the two viruses are in the same serogroup because on the outside they look very similar!

47
Q

which arbovirus has the most cases in the US?

A

West Nile virus

48
Q

what is the most common mosquito borne virus in North America?

A

WNV

reservoir = birds

vector = mosquitos

disease = encephalitis

flaviviridae family

49
Q

how can WNV be transmitted accidentally to someone?

A

blood transfusions!

so we have to make sure we’re really screening blood to make sure there’s nothing in blood transfusions we’re giving to people

50
Q

what are sentinels? what are the sentinels for WNV?

A

sentinel species are organisms, often animals, used to detect risks to humans by providing advance warning of a danger

WNV sentinels = horse, quail, turkey

51
Q

which population is at risk for WNV?

A

people over 50 years old

52
Q

what is the life cycle of the WNV?

A
  1. in the summer, the warm, wet weather produces large mosquito populations that then infect birds (some of which die)

mosquitos also infect dead-end hosts like horses and humans

  1. then in the fall, mosquito populations decline and birds migrate
  2. in the spring, the virus is amplified among birds and mosquitoes

this cycle just goes on and on

53
Q

which major disease is associated with WNV?

A

encephalitis!

WNV can effect the brain and cause direct cell killing of the neurons which causes serious mental status changes like bouts of confusion and disorientation

54
Q

what are the symptoms associated with WNV encephalitis?

A
  1. Subclinical
  2. Fever and headache
  3. Rash
  4. Meningitis
  5. Acute flaccid paralysis/poliomyelitis (rare)

eventually, symptoms can lead to seizures and comas

20% have mild symptoms

0.5% have severe symptoms

55
Q

what are some presenting symptoms of WNV?

A

A 54-year-old woman presented to our emergency department with a 4-day history of fevers, body aches, nausea and headache and a recently resolved rash. The patient’s mental status had progressively deteriorated with bouts of confusion and disorientation

  1. > 50 years old
  2. recently resolved rash (not always present though with WNV and it’s not diagnostic either)
  3. mental status deterioration = infection in the brain
56
Q

how do you treat WNV?

A

supportive care

there’s literally nothing we can do except hope that they will eventually restore their brain function as the virus clears

the problem is that sometimes by the time the virus has cleared, it’s already done severe brain damage to the patient

57
Q

which population is at a risk for Triple E?

A

bilateral distribution:

under 15 years old & over 50 years old

58
Q

what are the other viruses linked to Triple E?

A
  1. Triple E = Eastern Equine Encephalitis Virus
  2. there’s also Western equine encephalitis virus which has less cases and a lower CFR
  3. Venezuelan equine encephalitis virus where horses are the reservoir and it’s more mild
59
Q

is Triple E or WNV worse?

A

Triple E

this is because it can effect healthy, young individuals!

WNV is mostly in people over 50

60
Q

what are the characteristics of Triple E?

A

reservoir = birds

vector = mosquitos

disease = encephalitis

CFR = 35%

togaviridae family = Eastern Equine Encephalitis Virus

61
Q

what are the characteristics of the La Crosse Virus/California serogroup?

A

reservoir = small mammals ( chipmunks, squirrels, etc.)

vector = mosquito

disease = encephalitis

low CFR = <1%

bunyaviridae family = enveloped, helical (-) sense, segmented ssRNA

62
Q

which population is at risk for the La Crosse serogroup?

A

children

63
Q

what are the characteristics of the Powassan virus?

A

reservoir = small mammals

vector = ticks (Ixodes)

disease = encephalitis

flaviviridae family = enveloped, icasahedral (+) sense ssRNA

64
Q

why is Powassan virus underreported?

A

because it has the same tick/mammal host as lyme disease and there’s alot of overlapping symptoms

the Ixodes scapularis tick could be coinfected with lots of stuff and we don’t know how this effects the disease or its transmission

65
Q

which specific viruses are arboviruses associated with fever/hemorrhagic fever in the USA?

A

FLAVIVIRIDAE
1. Dengue virus

  1. Yellow fever virus
  2. Zika virus

TOGAVIRIDAE
1. Chikungunya virus

**all have mosquito vectors and primate reservoirs except Chikungunya which has small mammals, rodents, primates and birds as reservoirs

66
Q

what is the occurence, vector, reservoir and disease associated with Dengue virus?

A

disease = fever, HF, arthralgia

occurence = worldwide in tropical regions

vector = mosquito

reservoir = primates, humans

flaviviridae family = enveloped, icasahedral (+) sense ssRNA

67
Q

what is the occurence, vector, reservoir and disease associated with yellow fever virus?

A

disease = HF

occurence = south and central america

vector = Aedes mosquito

reservoir = primates, humans

flaviviridae family = enveloped, icasahedral (+) sense ssRNA

68
Q

what is the occurence, vector, reservoir and disease associated with zika virus?

A

disease = fever, rash, microcephaly

vector = mosquito

reservoir = primates, humans

flaviviridae family = enveloped, icasahedral (+) sense ssRNA

69
Q

what is the occurence, vector, reservoir and disease associated with Chikungunya virus?

A

disease = fever, arthralgia

occurence = worldwide in tropical regions

vector = mosquito

reservoir = small mammals and rodents, primates, birds

togaviridae family = enveloped, icasahedral (+) sense ssRNA

70
Q

what is the Sylvatic/Jungle Cycle?

A

arthropod —> vertebrate –> arthropod –> vertebrate –> etc.

or arthropod –> human

but the human isn’t part of the cycle because there isn’t enough virus in the blood for the mosquito to pick up and transmit to another host

ex. WNV: if there isn’t enough virus in the blood it won’t be picked up by mosquitos and transmitted

71
Q

what is the Urban cycle?

A

arthropod –> human –> arthropod –> human –> etc.

for some cycles, humans can be part of the cycle because there’s enough virus in the blood for the mosquito to pick up and transmit to another human

this is the urban cycle!

ex. Dengue virus

72
Q

what are the characteristics of the Dengue virus?

A

it’s an emerging disease

vector = mosquito (Aedes egyptei)

host = non-human primates

73
Q

is the Degnue virus a jungle or urban cycle?

A

both!

but for it to be an urban virus, it has to be under perfect conditions like 1000 people living in close quarters together with no screens like in underdeveloped areas

74
Q

what are the symptoms of the Dengue fever?

A
  • fever
  • headache
  • retro-orbital pain
  • myalgia/arthralgia
  • bone-ache (breakbone fever) because it infectd the BM = dengue 2
  • rash
  • flu-like illness
  • altered taste
  • RARELY: encephalitis
75
Q

what are the symptoms of the Dengue hemorrhagic fever/shock syndrome?

A

under certain conditions, Dengue can cause hemorrhagic fever/shock which includes symptoms such as:

  • thrombocytopenia since dengue infects the BM
  • hemorrhages
  • plasma leakage
  • hypotension
  • fluid accumulation in lungs
  • circulatory failure
  • renal failure!
  • shock
76
Q

what does ADE stand for?

A

antibody-dependent enhancement

77
Q

what is ADE and which virus is it associated with??

A

Dengue virus

viruses can be shutdown when antibodies bind to the virus and neutralize the virus

with Dengue, there are 4 circulating serotypes

so if you get infected with Dengue 1, you’ll generate antibodies against dengue 1 for your whole life

so if you are later exposed to Dengue 4, you aren’t protected because your neutralizing antibodies aren’t against dengue 4

the problem is that dengue 1 and 4 are similar enough that the original antibodies will still bind to dengue 4 without neutralizing and this actually makes it easier for the viruses to be taken up by certain cells which is super bad for us because it’s inhancing the infection!

the virus is getting into cells it wouldn’t normally infect and it’s doing better which can lead to a more severe secondary infection because non-neutralizing antibodies enhance the uptake of the virus into cells and accelerates the disease = ADE

this isn’t specific to dengue but it’s a big thing with dengue

this is also why we can’t really vaccinate against seperate dengue strains because people will get hemorrhagic fever when exposed to a different serotype of dengue!

78
Q

what do you have to avoid with ADE dengue patients?

A

aspirin and other anticoagulants

ADE dengue patients are probably in hemorrhagic shock and are already bleeding out so you shouldn’t be giving aspirin

79
Q

how do you treat Dengue fever?

A

there’s no treatment, just supportive treatment

Dengvaxia is the Dengue vaccine

it’s a live recombinant tetravalent vaccine

80
Q

how did yellow fever get its name?

A

the virus replicates specifically in the liver and destroys liver tissue so you get jaundice!!

81
Q

is yellow fever a jungle or urban cycle?

A

both!

82
Q

what are the symptoms of yellow fever?

A
  • hemorrhagic fever with jaundice
  • degeneration of liver, kidney and heart
  • thrombocytopenia
  • bleeding gums/stool
  • petechia
  • backpain
  • black blood vomit

CFR = 50%!!!!

83
Q

is there a vaccine against yellow fever?

A

yes!!

it’s a live attenuated travel vaccine

but if you already are having symptoms of HF and jaundice then it’s too late for you and you can’t get the vaccine; the vaccine is NOT a treatment!!

we have nothing to treat yellow fever once you get it…

84
Q

is the zika virus a jungle or urban cycle?

A

both!

85
Q

what are the symptoms of the zika virus?

A
  • mild fever

- rash

86
Q

what are some of the complications of zika virus?

A
  • birth defects (microcephaly)

- Guillain-Barre syndrome = a rare disorder in which your body’s immune system attacks your nerves

87
Q

what are the symptoms of the Chikungunya virus?

A
  • fever
  • headache
  • rash
  • joint pain = arthralgia