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Clinical Micro > Viral Hemorrhagic Fevers > Flashcards

Viral Hemorrhagic Fevers Flashcards

1
Q

What is VHF used to describe?

A

A host of viruses that cause severe, multi-organ, life-threatening disease

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2
Q

What are 3 common clinical manifestations of VHF?

A
  1. Fever + other non specific symptoms
  2. Shock
  3. Hemorrhage
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3
Q

What other nonspecific symptoms usually accompany fever?

A

headache, malaise, myalgias, arthralgias, abdominal pain, nausea, and diarrhea

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4
Q

What is occurring during shock?

A

body is not getting enough blood

- life threatening

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5
Q

is hemorrhagic bleeding usually life threatening?

A

no not the bleeding itself

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6
Q

Do you always see hemorrhage with VHFs?

A

no not always - most are not hemorrhagic in fact

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7
Q

How many virus families are primarily the cause of VHFs? what are they?

A
  1. Arenaviruses (ex. Lassa)
  2. Filoviruses (ex. Ebola)
  3. Bunyaviruses (ex. Hanta viruses)
  4. Flaviviruses (ex. Dengue)
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8
Q

What is a common structural/genomic feature of all VHF virus families?

A

All are enveloped RNA viruses

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9
Q

What containment level(s) are required to work with VHF causing viruses?

A

Mainly BSL4 but some are BSL3

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10
Q

VHF viruses rely on what kind of transmission and hosts?

A

They are zoonotic and therefore require reservoir hosts to survive
- from small mammals like rodents to large ones like monkeys

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11
Q

How does transmission of VHFs usually occur?

A

usually through animal or arthropod vectors

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12
Q

What are 2 typical animal vectors?

A

rodents or bats

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13
Q

What are 2 typical arthropod vectors?

A

ticks and mosquitos

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14
Q

What is the geographical distribution of VHF viruses like?

A

geographically restricted to areas where the hosts/vectors live

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15
Q

Which 3 Arboviruses cause Hemorrhagic fever in humans?

A
  1. Dengue fever
  2. Rift Valley fever virus
  3. Yellow fever virus
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16
Q

What are the major vectors for arboviruses?

A

mosquitos and ticks

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17
Q

What is the geographical distribution of Flaviviruses? What is the vector for them?

A

central and south america, india, south east asia, central africa
- aedes aegypti mosquito

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18
Q

What is the distribution of crimean congo hemorrhagic fever (CCHF)? What transmits it?

A

Mostly in Africa

- similar distribution to its vector, the Hyalomma sp of tick

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19
Q

What is the distribution of rift valley fever virus? whats the vector?

A

Africa mainly - Aedes is is the vector

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20
Q

Where are Hanta virus reservoirs?

A

north and south america, Europe, and China

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21
Q

Where’s the general distribution of Arenaviruses?

A

south america and parts of africa

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22
Q

Fruit bats of the Pteropodidae family for example are vectors of what type of viruses?

A

Filoviruses like Marburg and zaire ebola viruses

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23
Q

How frequent are the outbreaks or cases of VHFs in humans ?

A

they occur sporadically

24
Q

for primary VHF transmission, this usually occurs..

A

accidentally to humans - not the natural reservoir

25
Q

When do primary infections in humans tend to occur? What kinds of contact

A

when the activities of infected reservoir hosts or vectors and humans overlap

  • direct contact with rodent feces or urine for example
  • indirect through bites of mosquito or tick
  • direct contact during care or slaughter of animals
26
Q

How common is secondary transmission?

A

not that common among VHFs, only a couple of viruses have person-to-person transmission

ex: Lassa, Marburg, Ebola, CCHF

27
Q

How does secondary transmission typically occur?

A

direct close contact with infected people or their bodily fluids
- aerosol uncommon

28
Q

What are the 2 modes of transmission for Hantavirus?

A

aerosol or direct contact with abraded skin

29
Q

What is the vector of Hantavirus? How is the virus usually spread from them

A

Rodents

Spread indirectly through their feces or urine

30
Q

RVF virus is spread through what kind(s) of transmission?

A

primary only

31
Q

CCHF is spread through what kind(s) of transmission ?

A

primary and secondary

32
Q

Marburg is spread through what kind(s) of transmission ?

A

primary and secondary

33
Q

Ebola is spread through what kind(s) of transmission ?

A

primary and secondary

34
Q

How does primary transmission typically occur for Ebola?

A

Bats have high viral titre in feces and are then used as food

35
Q

How does secondary transmission occur for Ebola?

A

Direct contact with blood or secretions
- urine, feces, semen, breast milk

can occur through the mucosal or breaks in the skin

36
Q

Appropriate PPE for ebola needs to protect against…

A

contact, droplet,

need an N95 for aerosol generating procedures

37
Q

What is the incubation period for Ebola ?

A

up to 21 days but average is 11

38
Q

When do patients with Ebola not transmit?

A

when they are asymptomatic

39
Q

What are the 3 phases of Dengue Fever?

A
  1. Febrile phase
  2. Critical phase
  3. Recovery phase
40
Q

What are some symptoms of the febrile phase of dengue?

A

sudden onset fever, headache, mouth and nose bleeding, joint pain, vomiting, rash, diarrhea

41
Q

What are 4 features of the critical phase of dengue?

A

hypotension, pleural effusion, ascites, GI bleeding

42
Q

What are 4 features of the recovery phase of Dengue.

A

Altered LOC, seizures, itching, slow heart rate

43
Q

What is antibody dependent enhancement? (ADE)

A

When you get infected by one serotype of Dengue and then later infection by another serotype results in more severe disease because of antibodies that don’t completely neutralize the virus resulting in the virus being delivered into the wrong compartment in dendritic cells and therefore can replicate

44
Q

What are the 2 causes of death from ebola?

A

hypovolemic shock and multiorgan failure

45
Q

What is a “cytokine storm”

A

uncontrolled cytokine response

46
Q

what causes bleeding in the liver in most cases of VHF?

A

infection and necrosis of the liver combined with decreased clotting factors

47
Q

Fluid loss is usually a result of ..

A

increased vascular permeability

48
Q

Infection of cortical cells in the adrenal glands results in..

A

decreased production of steroids –> hypotension and then hypovolemic shock

49
Q

What is the mortality of Ebola vs Lassa vs Dengue ?

A

30-90% for ebola but most recent outbreak around 50%

Lassa: 15-25%

Dengue is 10%

50
Q

Diagnosis of VHF is based initially on..?

A

clinical criteria and judgment

51
Q

What are 4 lab based methods for confirming VHFs ? When are they used?

A

Serology - IgM and IgG, paired

acute/convalescent

Molecular: RT-PCR

Immunohistochemistry - tissues

Electron microscopy (EM) and viral culture 
-Extremely dangerous, only in BSL-4 labs if necessary
52
Q

For most VHFs, what are the 3 modes of treatment?

A
  1. Supportive care to manage symptoms
    - rehydration is key
  2. Antivirals but are not usually very effective
  3. Convalescent phase plasma
53
Q

Mostly there are no vaccines for VHFs except for?

A

Dengue, Argentine hemorrhagic fever, yellow fever

- Ebola is being developed

54
Q

What 2 families of viruses are of concern for being used as biological weapons?

A

Filoviruses and Arenaviruses

55
Q

Aerosolized VHF preparations are considered potentially suitable as biological weapons because..?

A
  1. Low infectious dose
  2. High morbidity and mortality
  3. Potential for person-to-person transmission
  4. Effective therapy and vaccines are not available

Clinical Micro (28 decks)

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