Infectious Diseases - Varicella Flashcards
What types of pathogen is varicella?
DNA
How is varicella spread?
Resp droplets and direct personal contact with vesicle fluid and indirectly via fomites
Sig contact 15 mins+, face to face, large open ward
When is varicella infectious?
48 hours before rash until crusted over
Primary chickenpox effects what number of pregnancies?
3/1000
What % of pregnancy women are sero+ve for IgG varicella?
90%
Which women are less likely to be immune to varicella?
Women from tropical and sub-tropical countries are less likely to be immune
Is reactivated herpes zoster infectious? Will is pass itoa-uterine?
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.
What are the maternal risks of varicella?
- 10% pneumonia - may require ventilation
- 3-14% mortality even with antivirals and ITU
Severity increases with increased gestation
Risk hepatitis & encephalitis
When does fetal varicella syndrome occur?
If sero conversation in 1st 28 weeks of pregnancy, rare between 20-28 weeks.
1% risk <28 weeks
What are the signs of symptoms of fetal varicella syndrome?
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
Can fetal varicella syndrome be diagnosed prenatally?
FMU USS at 16-20 weeks or 5 weeks after infection (limb deformity, microcephaly, hydrocephalus)
Amniocentesis has strong negative predictive value but poor positive
What should you ask in history to manage women who give history of contact with chickenpox or shingles?
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
If not immune and significant exposure to varicella?
Offer VZIG asap,, effective for 10 days after contact
Non immune women who have been exposed, how long should they be treated at infectious?
o 8-28 days after the exposure + receive VZIG
o 8-21 days after exposure if no VZIG
In what circumstance should a second dose of IVIG be given?
- 2nd dose of VZIG if further exposure is reported and 3 weeks since last dose
After exposure when should sero-conversion be tested for?
- 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
How to manage women who develop chicken pox in pregnancy?
- 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
What dose of acyclovir should be given?
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.
When should pregnancy women with chickenpox be referred to hospital?
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/
Women hospitalised from varicella should be isolated from which persons?
babies, pregnanct women and non immune staff
If delivery occurs in the varaemic period, what are the risks?
risk of bleeding, thrombocytopenia, DIC, hepatitis and a high risk of neonatal varicella with significant morbidity and mortality.
How long ideally should there be between onset of rash and delivery?
minimum of 7 days between onset of rash and delivery
Offer suppotive. Tx until delivery - allow passage of antibodies
How should women with varicella,
1) Delivery
2) Breastfeed
Can have SVD
Can breastfeed unless lesions near nipple (then express)
GA may exacerbated pneumonia
If epidural avoid area with lesions
If maternal infection of varicella in last 4 weeks of pregnancy, what % of babies are infection and what % develop clinical varicella
50% infected
23% clinical varicella
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)
Severe chickenpox if born within 7 days, give VZIG and IV acyclovir
VZIG has no benefit once neonatal developed varicella
Shingles at delivery?
No risk, as transplacental antibodies. Unless <28 weeks or <1kg as lack maternal antibodies
What should happened if fetal exposure in 1st 7 days of life?
- 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
If a neonates sibling has varicella and the mother is non immune, what should happen?
Delay discharge until the neonate is 7 days old
Is varicella immunisation a live vaccine?
Yes
Should only be given pre-pregnancy or post party to sero-negative mothers
How long does immunity last from the varicella vaccine?
20 years
