Varicella zoster virus (VZV)

Question 1

what is the mode of transmission?

Answer 1

• Airborne (from respiratory tract) (N95 required)

- Direct contact (from fresh skin lesions)

Question 2

What is the period of infectivity?

Answer 2

Period of infectivity: 2 days before rash onset, until skin lesions are at crusting stage

Question 3

what is the incubation period?

Answer 3

10-21 day. Administration of varicella-zoster immunoglobulin (VZIG) following exposure can prolong the incubation period up to 28 days.

Question 4

what are the clinical features of chicken pox?

Answer 4

1-2 day prodrome (may be absent in young children) -> fever, headache, malaise, pharyngitis, loss of appetite. Fever usually abates once rash has completely appeared

Vesicular rash: dewdrops on rose petals (clear vesicles on red papules)

• Rapid progression of rash (macules to papules to vesicles to pustules) in a matter of hrs
• The scalp, face, limb and trunk are all involved, with relatively sparing of palms and soles.
• Skin lesions at all stages of development may be seen on same area of skin
• Pustules crust and heal w/o scarring

Question 5

What are the complications of chicken pox?

Answer 5

Bacterial superinfection of skin lesions (e.g. group A Strep) – causing cellulitis

Pneumonia

• May begin 1-6 days after skin eruption
• Risk factors -> adults, cigarette smoking
• CXR shows diffuse changes throughout both lung fields

CNS

• Acute cerebellar ataxia (mainly in children)
• Diffuse encephalitis (mainly in adults)

Reye syndrome – in children mainly with aspirin use.

Hepatitis – generally occurs in immunosuppressed host.

Complications in pregnancy
- Early pregnancy (8-20wks) -> 2% risk of congenital malformation (congenital varicella syndrome)
- Later stages -> predisposes to herpes zoster of infant
5 days before to within 48hrs of delivery -> severe neonatal infection (give VZIG prophylaxis)

Question 6

What is the management of VZV?

Answer 6

• Symptomatic (uncomplicated disease) -> antihistamines, antipyretics
• Early treatment (within 24-48hrs of rash) & complicated disease -> PO acyclovir (800 mg 5x per day for 1/52)
• Immunosuppressed children -> IV acyclovir (if > 24hrs passed since symptom onset)

Question 7

someone have came into contact with a vzv+ person How do you post exposure prophylaxis?

Answer 7

Varicella vaccine PEP (post-exposure prophylaxis)
- 90% effective if given within 3 days of exposure to an immunocompetent individual (> 1 year old)

VZIG PEP (post-exposure prophylaxis)

• Susceptible immunocompromised (e.g. long-term corticosteroids)
• Susceptible pregnant women
• Newborns whose mothers had onset of varicella within 5 days before and 2 days post-delivery
• Preterm infants at ≥28 weeks gestation if mother is susceptible
• Preterm infants at <28 weeks gestation or ≤ 1kg, regardless of maternal serostatus

Question 8

how do shingles appear?

Answer 8

• First symptom: severe dermatomal pain that precedes rash
• Rash onset (vesicular lesions) distributed along a dermatome, ending at the midline
• In immunocompromised, rash may cross midline, or over multiple dermatomes (3 or more dermatomes)
• Virus may disseminate from fresh vesicles and cause chickenpox in susceptible contacts