Infectious Diseases - Varicella

Question 1

What types of pathogen is varicella?

Answer 1

DNA

Question 2

How is varicella spread?

Answer 2

Resp droplets and direct personal contact with vesicle fluid and indirectly via fomites

Sig contact 15 mins+, face to face, large open ward

Question 3

When is varicella infectious?

Answer 3

48 hours before rash until crusted over

Question 4

Primary chickenpox effects what number of pregnancies?

Answer 4

3/1000

Question 5

What % of pregnancy women are sero+ve for IgG varicella?

Answer 5

90%

Question 6

Which women are less likely to be immune to varicella?

Answer 6

Women from tropical and sub-tropical countries are less likely to be immune

Question 7

Is reactivated herpes zoster infectious? Will is pass itoa-uterine?

Answer 7

infectious but does not usually result in intra-uterine infection

The risk of acquiring infection from an immunocompetent individual with herpes zoster in a non-exposed site (such as thoraco-lumbar) is small. However, disseminated zoster, exposed zoster or localised zoster in an immuno-compromised individual should be considered infectious.

Question 8

What are the maternal risks of varicella?

Answer 8

• 10% pneumonia - may require ventilation
• 3-14% mortality even with antivirals and ITU
  Severity increases with increased gestation
  Risk hepatitis & encephalitis

Question 9

When does fetal varicella syndrome occur?

Answer 9

If sero conversation in 1st 28 weeks of pregnancy, rare between 20-28 weeks.

1% risk <28 weeks

Question 10

What are the signs of symptoms of fetal varicella syndrome?

Answer 10

One or more
1) Skin scarring - dermatomal

2) Eye defects(cataract/micropthalmia/retinitis)

3) Limb hypoplasia

4) Mental retardation with cortical atrophy

5) Sphincter dysfunction

No increased risk 1st trimester miscarriage

Question 11

Can fetal varicella syndrome be diagnosed prenatally?

Answer 11

FMU USS at 16-20 weeks or 5 weeks after infection (limb deformity, microcephaly, hydrocephalus)

Amniocentesis has strong negative predictive value but poor positive

Question 12

What should you ask in history to manage women who give history of contact with chickenpox or shingles?

Answer 12

1) Ascertain diagnosis of varicella, infectiousness and degree of exposure.

2) If uncertain/no history or chickenpox or from tropical/subtropical country - take blood to determine immunity

80% will have immunity

Question 13

If not immune and significant exposure to varicella?

Answer 13

Offer VZIG asap,, effective for 10 days after contact

Question 14

Non immune women who have been exposed, how long should they be treated at infectious?

Answer 14

o 8-28 days after the exposure + receive VZIG
o 8-21 days after exposure if no VZIG

Question 15

In what circumstance should a second dose of IVIG be given?

Answer 15

• 2nd dose of VZIG if further exposure is reported and 3 weeks since last dose

Question 16

After exposure when should sero-conversion be tested for?

Answer 16

• Check for sero-conversion (VZ IgM 3 weeks after exposure). If chickenpox develops, she should be advised to avoid contact with others at risk including other pregnant women and counselled about the risk of fetal varicella syndrome

Question 17

How to manage women who develop chicken pox in pregnancy?

Answer 17

• Advise women to contact their GP immediately if they develop a rash
• Advise to avoid contact with susceptible individuals (other pregnant women and neonates), until the lesions have crusted over (~5 days after the onset of the rash).
• Symptomatic treatment and hygiene to prevent secondary bacterial infection of the lesions.
• Oral aciclovir if they present within 24 hours of the onset of the rash and if >20 weeks gestation. Aciclovir should be used cautiously before 20 weeks

Question 18

What dose of acyclovir should be given?

Answer 18

800mg x 5 for 7 days reduced duration fever and symptoms if started within 24 hours

Not associated with fetal anomalies although there is a theoretical risk of terratogenesis in the first trimester.

Question 19

When should pregnancy women with chickenpox be referred to hospital?

Answer 19

Referred immediately to a hospital if the following develop: chest symptoms, neurological symptoms, haemorrhagic rash or bleeding, a dense rash with or without mucosal lesions.Women with significant immunosuppression should also be referred.

If high risk should be assessed even in absence of concerning features -smoker, chronic lung disease, immunocompromised (systemic steroids > 3months), 2nd half of pregnancy/

Question 20

Women hospitalised from varicella should be isolated from which persons?

Answer 20

babies, pregnanct women and non immune staff

Question 21

If delivery occurs in the varaemic period, what are the risks?

Answer 21

risk of bleeding, thrombocytopenia, DIC, hepatitis and a high risk of neonatal varicella with significant morbidity and mortality.

Question 22

How long ideally should there be between onset of rash and delivery?

Answer 22

minimum of 7 days between onset of rash and delivery

Offer suppotive. Tx until delivery - allow passage of antibodies

Question 23

How should women with varicella,
1) Delivery
2) Breastfeed

Answer 23

Can have SVD
Can breastfeed unless lesions near nipple (then express)

GA may exacerbated pneumonia
If epidural avoid area with lesions

Question 24

If maternal infection of varicella in last 4 weeks of pregnancy, what % of babies are infection and what % develop clinical varicella

Answer 24

50% infected
23% clinical varicella

Question 25

What is the risk and what should be done if born within 7 days of material infection (either 7 days before delivery or 7 days after)

Answer 25

Severe chickenpox if born within 7 days, give VZIG and IV acyclovir

VZIG has no benefit once neonatal developed varicella

Question 26

Shingles at delivery?

Answer 26

No risk, as transplacental antibodies. Unless <28 weeks or <1kg as lack maternal antibodies

Question 27

What should happened if fetal exposure in 1st 7 days of life?

Answer 27

• If there is contact with chickenpox in the first 7 days of life, no intervention is required if the mother is immune. However, the neonate should be given VZIG if the mother is not immune to varicella or if the neonate delivered before 28 weeks or weighs <1kg

Question 28

If a neonates sibling has varicella and the mother is non immune, what should happen?

Answer 28

Delay discharge until the neonate is 7 days old

Question 29

Is varicella immunisation a live vaccine?

Answer 29

Yes
Should only be given pre-pregnancy or post party to sero-negative mothers

Question 30

How long does immunity last from the varicella vaccine?

Answer 30

20 years