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CELL MICRO S1 > Viruses that cause haemorrhagic fever > Flashcards

Viruses that cause haemorrhagic fever Flashcards

1
Q

haemorrage is fluid leakage from what?

A

capillaries- thinner vessels, allows access to mosquitos

- single layer of endothelial cells, this barrier is maintained by PERICYTES

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2
Q

what is haemorrhage?

A

the escape of blood from any blood vessel in body

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3
Q

what does viral haemorrage cause?

A
  • severe multi-system syndrome characterised by diffuse vascular leakage
  • often bleeding (may/may not be life threatening)
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4
Q

give examples of viral haemorrage effects?

A
  • bruises
  • conjuctival inf (esp Dengue)
  • epistaxis (nose bleed)
  • petechie (nose bleed, esp Dengue)
  • edema
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5
Q

give 2 examples of haemorrhagic blood borne viruses?

A
  • Ebola
  • Marburg
    FILOVIRUSES
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6
Q

give an example of haemorrhagic airborne viruses?

A

Lassa virus

ARENAVIRUSES

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7
Q

give an example of haemorrhagic arthropod-borne viruses?

A

Dengue

FLAVIVIRUS

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8
Q

what is the family and genus of Ebola virus? what is the family and genus of Marburg virus?

A

Family Filoviridae

Genus Ebolavirus, Maburgvirus

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9
Q

what is the tropism of Ebola and Marburg?

A

immune cells (macrophages), hepatocytes, endothelia cells (then can cause haemorrhage)

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10
Q

what type of infection is caused by Ebola and Marburg? is there persistence?

A
  • severe acute infection

- persistence can lead to future disease

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11
Q

what are the treatments/vaccines for Ebola/Marburg? Are there any?

A

no treatments/vaccines

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12
Q

how did Marburg end up in Germany?

where is Marburg virus found?

A

research using non human primates from Africa which carried Marburg virus found in Germany
- found normally in Angola, DRC recently in Uganda

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13
Q

where is Ebola found?

what is the most common Ebola?

A

Sudan, DRC

- most common is Zaire Ebola

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14
Q

Reston ebola is found where?

A

Philippines

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15
Q

why does the Ebola virus change from the original virus?

A

mutations cause evolution

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16
Q

what is the enzootic (wildlife) cycle for Ebola and MArburg?

A

animal reservoir in Pteropodiae

fruit BATS, megabats

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17
Q

what is the epizootic (wildlife) cycle for Ebola and MArburg?
how does this spillover to humans ?

A

infects non human primates (gorillas) and antelopes (Duikers)
at this point it can spillover into humans (go to forest for Bushmeat)

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18
Q

how is ebola transmitted?

how long is the incubation period?

A 
- via body fluids (blood and others)
(living and dead people)
- sexual contact
- contaminated surfaces
INCUBATION PERIOD: 2-21 days
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19
Q

how does ebola progress and what symptoms does it cause?

A

day 7-9= headache, fatigue, muscle soreness
day 10= sudden high fever, vomiting blood, passive behaviour
day 11= bruising, brain damage, bleeding from nose, mouth anus
dau 12= FINAL STAGES
loss of consciousness, seizures, massive internal bleeding DEATH

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20
Q

what is the death rate for Ebola?

A

7 days after onset of symptoms =30% chance of surviving

3 weeks after symptoms= 90% chance of surviving

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21
Q

where can Ebola persist and what does this cause?

A 
areas the immune system cannot reach
TESTES- can enable sexual transmission
EAR- hearing loss
EYE- retro orbital pain, blurred vision 
BRAIN/CNS- meningitis
UTERUS- transmission to fetus, stillbirth 
MUSCLE/JOINT- myalgia
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22
Q

how does Ebola cause haemorrage via cytokines?

A

immune distruption–> infects immune cells–> i.s responds by producing cytokines (POSITIVE FEEDBACK LOOP)—> HIGH levels of VASODILATORY cytokines—> allows opening up of vasculature to allow immune cells to enter tissues—> but the level of vasodilatory cytokines are too high O blood leakage—> haemorrhage

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23
Q

what are 2 other ways (other than cytokines) that ebola can cause haemorrhage?

A

1) direct infection of ENDOTHELIAL cells
2) infection of LIVER, this disrupts production of coagulase factors for clotting
3) infection of ADRENAL glands and KIDNEY, dirupts balance of blood pressure

24
Q

in airborne viruses, do large or small droplets travel further?

A

small (>10m)

25
Q

what is the family and genus of Lassa virus?

A

Arenaviridae Arenavirus

26
Q

what is the tropism of Lassa virus?

A

broad, infects many organs and tissues

27
Q

what kind of infection does LAssa virus cause?

A

acute, not persistent

28
Q

around how many Lassa inf occur every year?

A

2 million

29
Q

are there any vaccines/treatment for Lassa virus?

A

no

30
Q

how is Lassa virus transmitted?

A

rodents

31
Q

what are the 2 branches of Arenaviruses? where are they found?

A

Old World- Africa

New World- Americas

32
Q

where is Lassa virus found?

A

in West Africa

33
Q

how is Lassa virus transmitted?

how is it transmitted from human-human?

A
  • horizontal (between individuals) or vertical (from mother-> infant) transmission
  • humans infected by INHALING AEROSOLISED FAECES also eating infected rodents

human-human (20%)

  • sexual transmission
  • contaminated medical equipment
34
Q

what is the reservoir for Lassa infection?

A

rodents - Mastomys natalensis (multimammate rat)

35
Q

what % of people have severe Lassa symptoms? what are the symptoms?

A

20%
Symptoms: general (fever, headache, sore throat, vom, diarrhoea)—> face swelling, low bp (due to blood leak from CVS), nose bleeds (CRITICAL)

36
Q

how common is haemorrhage in Lassa? how severe is haemorrhage?

A

uncommon (~17%)

not severe enough to directly cause death

37
Q

what causes haemorrhage in Lassa?

A
  • dysfunction of PLATELETS and COAGULATION CASCADE
  • virus replication in ENDOTHELIAL cells(doesn’t kill cells)
  • NO CYTOKINE STORM
38
Q

what is the primary cycle of transmission used by Dengue?

A

urban epidemic cycle
(human-mosquito-human)
- driven by: the mosquitos that cause Dengue are in close association with humans

39
Q

what family and genus is Dengue virus? what are the serotypes of Dengue?

A

Flaviviridae Flavivirus

4 serotypes: DENV-1, DENV-2, DENV-3, DENV-4

40
Q

what is the tropism of dengue?

A 
immune cells (macrophages, dendritic cells)
- can also infect hepatocytes and endothelial cells
41
Q

what kind of infection does Dengue cause?

A

acute infection, no persistence

42
Q

what transmits Dengue?

A

Ae. aegypti and Ae. albopictus mosquitoes

43
Q

why is Dengue significant?

A

MOST SIGNIFICANT ARBOVIRUS INFECTING HUMANS

2.5 BILLION in high risk areas

44
Q

what are the symptoms of Dengue?

A
  • high persistant fever
  • severe headache
  • rash/mild bleeding (nose, gums, easy bruising)
  • joint, muscle and bone pain
  • severe pain BEHIND EYE
45
Q

how does Dengue progress?

A

day -4 = day of mosquito bite
day -1 = VIRAEMIA develops and is DETECTABLE
day 0= day of fever
day 4= RISK OF SHOCK AND HAEMORRHAGE (12 hr period)

46
Q

how many people does Dengue infect per year?

A

400 million

96 asymptomatic
1/2 million haemorrhagic (20% are fatal)

47
Q

what is the biggest risk factor for Dengue Haemorrhagic Fever/ Dengue Shock Syndrome?

A

SEQUENTIAL INFECTION W/ DIFFERENT SEROTYPES

48
Q

what happens if you only have primary dengue of 1 serotype?

A

low risk of haemorrhage

  • life long immunity against the serotype you were infected with
  • short term immunity against the other serotypes
49
Q

what happens if you have primary dengue and then get reinfected with the same serotype as a secondary inf?

A

low risk of haemorrhage

50
Q

what happens if you have primary dengue and then get reinfected with A DIFFERENT serotype as a secondary inf?

A

increased viral levels in patient blood

  • high risk of haemorrhage
  • life long immunity against all 4 serotypes
51
Q

what is hyperendemicity?

A

multiple dengue virus serotypes co-circulating in the same location

52
Q

how have vectors affected dengue circulation?

A

vector control methods can decrease the incidence of disease, eg Ae.aegypti

53
Q

how is Dengue treated?

A
  • no antiviral therapies

can treat with fluid replacement to prevent cirulatory collapse

54
Q

is there a dengue vaccine? how effective is it? where is it used?

A

yes,
partially effective, but CAN ENHANCE DISEASE
- cont all 4 serotypes
- used in highly endemic countries Philippines, Mexico

55
Q

who is given the dengue vaccine?

A
  • children 9+
    at this age children are usually already exposed to dengue O it provides lifelong immunity
  • mimics secondary inf w/ different serotype
56
Q

how does dengue cause haemorrhage?

A
  • cytokine storm(esp vasodilatory)
  • pot inf of endothelial
  • viral protein NS1 can DIRECTLY cause h
    (can be used for diagnosis), causes endothelial cells to open up

CELL MICRO S1 (16 decks)

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