varicella-zoster virus (chickenpox/shingles)

Summary for ED clinicians:

isolate patients from others including those in the ED waiting room
antivirals for clinical varicella:
- high risk patients (incl. pregnant, immunocompromised, age < 28 days, or very unwell) with clinical chickenpox should be considered for aciclovir, and perhaps consider also for those over the age of 12yrs if within 24hrs of rash
  - admit for iv aciclovir if either:
    - neonatal chickenpox and either:
      - mother developed chickenpox within 7 days prior to delivery or within 28 days after delivery
      - unwell, poor feeding, or tachypnoeic
      - immunocompromised
      - premature (<28wks gestation)
      - on corticosteroids
      - less than 7 days old when exposed
    - non-neonates (including adults) with chickenpox and either:
      - immunocompromised
      - altered mental state (?encephalitis)
      - respiratory symptoms and CXR suggests pneumonia
  - patients with shingles should be considered for aciclovir if within 72hrs of onset.
post-exposure prophylaxis for non-immune contacts:
- non-immune contacts who are immunocompromised, pregnant or neonates should be considered for ZIG within 96hrs post-exposure
  - neonatal indications for post-exposure ZIG (ie. age < 28 days):
    - neonatal age < 96hrs and mother developed chickenpox within 7 days of delivery
    - neonate aged < 7 days and born < 28wks gestation OR mother seronegative or unknown immune status for varicella
    - immunocompromised neonate and no immunoglobulin within last 3 weeks and no PH chickenpox¹⁾
- non-immune adolescent and adult contacts who are not pregnant nor immunocompromised should be offered post-exposure varicella vaccination if within 5 days of contact
- whilst the notes below refer to aciclovir, in non-pregnant adults, other antivirals can be used instead which allow tds oral dosing rather than 5x/day dosing, examples include famciclovir 250mg (500mg for immunocompromised), and valaciclovir 1g. The course should be for a minimum of 10 days.

introduction

varicella-zoster virus (VZV or human herpesvirus type 3) is a DNA virus within the herpes virus family.
it is a highly contagious infection spread by air-borne transmission of droplets from the upper respiratory tract or from the vesicle fluid of the skin lesions of varicella or zoster infection
The period of infectivity is from 48 hours before the onset of rash until crusting of all lesions has occurred.
primary infection with VZV causes varicella (chickenpox)
- this is usually mild in immunocompetent children over age 28 days with only 1% developing complications.
- it is more severe in adults and in individuals of any age with impaired immunity, in whom complications, disseminated disease, and fatal illness can occur.
- average incubation period is 14 to 16 days (range 10–21 days), but may be longer in those with impaired immunity, especially after receipt of zoster immunoglobulin (ZIG).
- acute varicella may be complicated by:
  - secondary bacterial skin infection - may warrant Rx with iv flucloxacillin, especially in neonates with cellulitis
  - pneumonia
  - acute cerebellar ataxia (1 in 4000 cases)
  - aseptic meningitis
  - transverse myelitis
  - encephalitis (1 in 100 000 cases)
  - thrombocytopenia
  - rarely, it involves the viscera and joints
- congenital varicella syndrome has been reported after varicella infection in pregnancy
  - may result in skin scarring, limb defects, ocular anomalies, and neurologic malformations
  - higher risk to the fetus if maternal infection occurs in the second trimester compared with infection in the first trimester (1.4% vs 0.55%)
  - infants with intrauterine exposure also risk developing herpes zoster in infancy (0.8–1.7%) with the greatest risk following exposure in the third trimester
- severe neonatal varicella infection can result from perinatal maternal varicella
  - onset of varicella in pregnant women from 5 days before delivery to 2 days after delivery is estimated to result in severe varicella in 17 to 30% of their newborn infants
following primary infection, VZV establishes latency in the dorsal root ganglia.
latent reactivation results in herpes zoster (shingles)
varicella in the nonimmune can be modified or prevented following exposure to an infected patient either by the use of varicella vaccine given within 5 days of exposure or by the administration within 96 hours of exposure of high-titre varicella-zoster immunoglobulin (ZIG). The latter product is available on a restricted basis from the Australian Red Cross Blood Service for the prevention of varicella in high-risk nonimmune, such as the immunocompromised and pregnant women who are close to term.²⁾

indications for aciclovir

Australian PBS authority 2011 approved indications for varicella/zoster

herpes zoster within 72hrs of onset of rash (800mg tabs x 35)
herpes zoster ophthalmicus (800mg tabs x 35)

Australian Therapeutic Guidelines indications 2011

pregnant women with varicella within 72hrs of onset of rash
immunocompromised patients with varicella irrespective of duration of rash
- NB. infants aged < 28 days are regarded as immunocompromised by paediatricians
- ATG - varicella in HIV patients
normal patients with severe chickenpox (eg. pneumonitis, encephalitis or hepatitis) irrespective of duration of rash
NB. if severe disease, start with iv aciclovir 10mg/kg 8h (adjust for renal function) then change to oral 800mg (20mg/kg to max 800mg) 5 times a day.

varicella vaccination

varicella vaccine should not be given during pregnancy and vaccinees should not become pregnant for 28 days after vaccination.
varicella-containing vaccines are contraindicated in subjects with primary or acquired impaired immunity eg. HIV, leukaemia, lymphoma, high dose immunosuppressives such as corticosteroids, etc.
varicella-containing vaccines should not be given for between 3 and 9 months after the administration of immunoglobulin-containing blood products.

varicella vaccination is now recommended for children and non-immune adolescents and adults
vaccination is well tolerated in previously infected individuals and can be administered if there is uncertainty regarding immunity.
testing to check for seroconversion after varicella vaccination is not recommended.
adolescents and adults require 2 doses at least 4 weeks apart
vaccination is particularly recommended for³⁾:
- non-immune people in high-risk occupations where exposure to varicella is likely (such as healthcare workers, teachers and workers in childcare centres)
- non-immune women before pregnancy to avoid congenital or neonatal varicella
- seronegative women immediately after delivery
- non-immune parents of young children
- non-immune household contacts of all ages of people with impaired immunity.

Mx of non-immune contacts post-exposure

post-exposure varicella vaccination

see warnings under vaccination above!!

post-exposure vaccination can be considered for those at high risk who have not had prior exposure to chickenpox nor had vaccination.
varicella vaccination is generally successful when given within 3 days, and up to 5 days, after exposure, with earlier administration being preferable.
In the event of an outbreak, seek advice from local public health authorities before proceeding with vaccination of a large number of individuals
Australian Govt varicella vaccination guidelines

indications for post-exposure ZIG

in high risk individuals in whom active vaccination is contraindicated (eg. pregnancy, immunocompromised and neonates), consider Zoster Immunoglobulin (ZIG)
- ZIG must be given within 96hrs of exposure to be effective although can be given up to 10 days post-exposure in immunocompromised patients⁴⁾
- ZIG must be given IM.
- it is available from the Australian Red Cross Blood Service on a restricted basis
- dose of ZIG: < 20kg: 200 IU; 20-30kg: 400 IU; > 30kg: 600 IU;
- ZIG need not be given to an immune impaired contact of a vaccinee with a rash because the disease associated with this type of transmission (should it occur) would be expected to be mild.

neonates

neonatal indications for post-exposure ZIG (ie. age < 28 days):
- neonatal age < 96hrs and mother developed chickenpox within 7 days of delivery
- neonate aged < 7 days and born < 28wks gestation OR mother seronegative or unknown immune status for varicella
- immunocompromised neonate and no immunoglobulin within last 3 weeks and no PH chickenpox⁵⁾

non-immune health care workers

If the patient is a health care worker (HCW) and is vaccinated after exposure, he/she can work but should watch daily for any rash for 6 weeks after exposure. Note that the VV-associated rash may be atypical, maculopapular and non-vesicular. If a varicella-exposed and vaccinated HCW develops a rash following vaccination, this may be due to either wild-virus or vaccine-strain varicella-zoster virus. In the event of a rash after vaccination, cover the rash, reassign duties (no patient contact) or place on sick leave until no new lesions appear and all lesions have crusted.
If an exposed non-immune HCW does not accept vaccination, reassign duties or place on sick leave from days 10 to 21 from the time of first exposure.

Mx of post-exposure vaccinees in non-health care workers

If vaccinees develop a rash, they should cover the rash and avoid contact with people with impaired immunity for the duration of the rash.
- Zoster immunoglobulin (ZIG) need not be given to an immune impaired contact of a vaccinee with a rash because the disease associated with this type of transmission (should it occur) would be expected to be mild.

¹⁾ , ⁵⁾

RCH guideline

²⁾

ATG 2011

³⁾

http://immunise.health.gov.au/internet/immunise/publishing.nsf/Content/Handbook-varicella|Australian Govt varicella vaccination guidelines]]

⁴⁾

Aust. vaccination guidelines