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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
What test would you do to see if someone is immune to VZV?
Test for VZV IG via colorimetry/fluorescent substrate
26
What does the presence of VZV IgG in serum indicate?
Marker of prior infection Indicates protective immunity
27
What should be prescribed to pregnant women who are VZV IgG negative and exposed to the virus?
VZIG Varicella Zoster ImmunoGlobulin
28
What is VZIG made of?
Pooled plasma from non UK donors with high titre of anti VZV IgG
29
Do you have to present with chickenpox to have been exposed to the virus?
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
What is the aim of VZIG?
Reduce severity of maternal disease Reduce of risk of foetal infection
31
When is VZIG given?
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
What is another cause, other than shingles, of vesicular rashes?
HSV
33
What is a way to distinguish between HSV and VZV?
PCR
34
What happens when a patient in a transplant ward develops shingles?
Isolated Treated with acyclovir
35
What happens to the patients in the transplant ward exposed to the patient with shingles?
Test for VZV IgG IgG negatives: give VZIG and isolate
36
What type of vaccine is the chickenpox vaccine?
Live attenuated
37
To who is the chickenpox vaccine recommended for?
Healthcare workers Regular/ close contacts of person at high risk from VZV
38
Why has the UK opted out of making chickenpox vaccine widespread?
Exposure to varicella boosts immunity to herpes-zoster Highly protective If remove the varicella = less protected against shingles
39
What has recently happened in the incidence of zoster?
Incidence of zoster is increasing No change to rate after vaccination programme started So vaccine is useless in protecting against shingles
40
What is the current vaccine used to protect against Zoster?
Zostavax
41
When is Zostavax taken?
Adults aged 70 years Catch-up for adults aged 78 and 79
42
What is a vaccine that is currently being investigated and predicted to have better results than the Zostavax vaccine?
Herpes Zoster Subunit vaccine
43
What is tested to reveal someone's history to exposure to VZV?
Antibody ELISA
44
What is tested to reveal current infection of VZV?
DNA/antigen PCR
45
What is the benefit of the virus being in latent stage?
Allows it to survive months immune response Can wait for another host and reactivate
46
Why does the virus become latent in nerve ganglia?
No tissue turnover in neurons
47
How does the virus exist during the latent stage?
Sits as an episomal DNA molecule
48
Where are rashes originating from shingles occur most commonly?
In the waist
49
Why were post-mortem examinations of nerves to look at latent stage of virus ineffective?
Death is physiologically stressful Would reactivate the virus
50
What technique was used to identify genes responsible for latency?
RNA transcriptome

PPS - infections (8 decks)

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