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PPS - infections > Varicella Zoster Virus > Flashcards

Varicella Zoster Virus Flashcards

1
Q

What is chickenpox?

A

Varicella zoster virus

Belong to the family of Alpha herpes viruses

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2
Q

When does chickenpox normally present?

A

Normally a mild illness of childhood

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3
Q

What percentage of UK-raised adults are immune to chickenpox?

A

> 90%

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4
Q

What is the genome of varicella zoster virus?

A

ds DNA genome

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5
Q

How many base pairs does the genome of the varicella zoster contain?

A

130 000 base pairs

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6
Q

What happens during primary infection of chickenpox?

A

Viral replication in skin causes lesions

This presents as chickenpox

Immune control regulates this

Retrograde spread in sensory neurons

Latency is established in the ganglion

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7
Q

Where is latency established?

A

In the ganglion

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8
Q

What happens during reactivation of the varicella zoster virus?

A

Reaction from latency induced by unknown factors

Anterograde spread

Viral replication in skin causes lesions to develop and presents as shingles

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9
Q

What does reaction of varicella zoster present as?

A

Shingles

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10
Q

To who are herpesviruses problematic?

A

In immunocompromised individuals

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11
Q

Examples of immunocompromised individuals

A

HIV

Transplantation

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12
Q

Zoster lesions are usually limited to a single dermatome

TRUE or FALSE

A

TRUE

Area innervated by sensory neuron that contains latent form of the virus

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13
Q

Which percentage of chicken pox patients develop Zoster?

A

25-35%

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14
Q

What factor increase the incidence and severity of Zoster?

A

Age

Immune senescence

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15
Q

Chickenpox is a special risk to pregnant women, foetus and neonates

TRUE or FALSE

A

TRUE

Risk of fatal varicella is five times higher in pregnant women

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16
Q

During which time of the pregancy is material infection most risky to the foetus/neonate?

A

First 20 weeks: Congenital varicella syndrome (1-2% pregnancies)

Second and third trimesters: Neonatal Zoster

A week before to a week after delivery: Severe/fatal neonatal disease

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17
Q

Is chickenpox contagious?

A

Yes, highly contagious

Not determined what the main mode of transmission for the virus is

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18
Q

What is the chance of getting chickenpox through household contact?

A

100%

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19
Q

What is the first step to do if a mother presents to a neonatal clinic with a child sick with chickenpox?

A

Urgent look back at clinic list for possible contacts

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20
Q

What characterises people who have had contact with the child?

A

Face-to-face contact

15 minutes in the same room

Two hours before/after the woman’s appointment

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21
Q

When we have identified the women at risk of exposure, what are the next steps?

A

Retrieve stored sera

Taken for routine screening tests done in pregnant women

22
Q

What is a mother has Hepatitis B?

A

Vaccine and Ig for baby

Potentially fatal to the embryo

23
Q

What is a mother has Syphilis?

A

Antibiotics for mum

And baby if needed

Potentially fatal to the embryo

24
Q

What is a mother has HIV?

A

ART for mum

No breastfeeding

1 month AZT for baby

Potentially fatal to the embryo

25
Q

What test would you do to see if someone is immune to VZV?

A

Test for VZV IG via colorimetry/fluorescent substrate

26
Q

What does the presence of VZV IgG in serum indicate?

A

Marker of prior infection

Indicates protective immunity

27
Q

What should be prescribed to pregnant women who are VZV IgG negative and exposed to the virus?

A

VZIG

Varicella Zoster ImmunoGlobulin

28
Q

What is VZIG made of?

A

Pooled plasma from non UK donors with high titre of anti VZV IgG

29
Q

Do you have to present with chickenpox to have been exposed to the virus?

A

No

11% of children aged 1 to 5 years,

37% aged 6 to 16 years

89% of adults

With a negative history of chickenpox are VZV IgG positive

30
Q

What is the aim of VZIG?

A

Reduce severity of maternal disease

Reduce of risk of foetal infection

31
Q

When is VZIG given?

A

Infants whose mothers develop chickenpox in the period seven days before to seven days after delivery

VZV antibody-negative infants exposed to chickenpox or zoster in the first 7 days of life

32
Q

What is another cause, other than shingles, of vesicular rashes?

A

HSV

33
Q

What is a way to distinguish between HSV and VZV?

A

PCR

34
Q

What happens when a patient in a transplant ward develops shingles?

A

Isolated

Treated with acyclovir

35
Q

What happens to the patients in the transplant ward exposed to the patient with shingles?

A

Test for VZV IgG

IgG negatives: give VZIG and isolate

36
Q

What type of vaccine is the chickenpox vaccine?

A

Live attenuated

37
Q

To who is the chickenpox vaccine recommended for?

A

Healthcare workers

Regular/ close contacts of person at high risk from VZV

38
Q

Why has the UK opted out of making chickenpox vaccine widespread?

A

Exposure to varicella boosts immunity to herpes-zoster

Highly protective

If remove the varicella = less protected against shingles

39
Q

What has recently happened in the incidence of zoster?

A

Incidence of zoster is increasing

No change to rate after vaccination programme started

So vaccine is useless in protecting against shingles

40
Q

What is the current vaccine used to protect against Zoster?

A

Zostavax

41
Q

When is Zostavax taken?

A

Adults aged 70 years

Catch-up for adults aged 78 and 79

42
Q

What is a vaccine that is currently being investigated and predicted to have better results than the Zostavax vaccine?

A

Herpes Zoster Subunit vaccine

43
Q

What is tested to reveal someone’s history to exposure to VZV?

A

Antibody

ELISA

44
Q

What is tested to reveal current infection of VZV?

A

DNA/antigen

PCR

45
Q

What is the benefit of the virus being in latent stage?

A

Allows it to survive months immune response

Can wait for another host and reactivate

46
Q

Why does the virus become latent in nerve ganglia?

A

No tissue turnover in neurons

47
Q

How does the virus exist during the latent stage?

A

Sits as an episomal DNA molecule

48
Q

Where are rashes originating from shingles occur most commonly?

A

In the waist

49
Q

Why were post-mortem examinations of nerves to look at latent stage of virus ineffective?

A

Death is physiologically stressful

Would reactivate the virus

50
Q

What technique was used to identify genes responsible for latency?

A

RNA transcriptome

PPS - infections (8 decks)

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