varicella

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
  • 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

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.
varicella.txt · Last modified: 2013/07/09 04:41 by gary1