varicella
Table of Contents
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
- 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.
3)
http://immunise.health.gov.au/internet/immunise/publishing.nsf/Content/Handbook-varicella|Australian Govt varicella vaccination guidelines]]
varicella.txt · Last modified: 2013/07/09 04:41 by gary1
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