Varicella Zoster Virus

Disclaimer

These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.

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Aim

To guide staff with respect to the assessment and management of disease due to varicella zoster virus (VZV).

Definition

Varicella zoster is a highly infectious DNA virus from the herpes virus family which causes chickenpox in primary infections
It can also establish latency in dorsal nerve root ganglia and be reactivated causing shingles (Herpes zoster)
There is only one serotype, and humans are the only reservoir.

Background

In immunocompetent children, particularly those vaccinated, chickenpox is generally a benign and self-limiting illness.
Hospitalisation is rarely required in uncomplicated chickenpox.
Primary VZV infection during pregnancy may result in severe disease in the mother and/or foetal varicella syndrome if transplacental infection occurs prior to 28 weeks gestation.
Vaccination is highly effective in preventing severe VZV infection. However up to 15-20% of vaccinated children may still develop a mild illness if subsequently exposed to VZV.
Shingles is relatively uncommon in children but is more common if the original infection occurred in the first year of life.
Incubation and infectivity. The incubation period is usually 14 to 16 days (range 10 to 21 days).
Incubation is shorter in immunocompromised patients and in neonates infected perinatally.
Incubation may be prolonged (up to 28 days) in patients and in neonates infected perinatally.
In immunocompromised patients the illness, and period of infectivity, is prolonged, and the patient should be considered infectious as long as new vesicles continue to appear.
All varicella zoster infections (chickenpox and shingles) are notifiable diseases under the Public Health Act 2016.

Risk factors

Patients at risk of severe primary disease:

Non-immune adults and adolescents over 15 years of age
Pregnant women (non-immune)
Neonates
Immunocompromised children and adults.

Assessment

Primary varicella infection (chickenpox) may be asymptomatic.
Symptomatic children have mild fever, anorexia and lethargy, followed by an itchy vesicular skin rash for 3 to 5 days.
Crops of papules appear initially, quickly becoming vesicular, then rupturing, leaving a crusted lesion. These are more concentrated over the trunk than the limbs but can occur anywhere. Lesions often have significant surrounding erythema as they crust over.

Observations

Baseline observations include heart rate, respiratory rate and temperature. Blood pressure, saturations and neurological observations if clinically indicated (if unsure consult with clinical nurse or doctor).
Minimum of hourly observations should be recorded whilst in the Emergency Department (ED).
Any significant changes should be reported immediately to the medical team.

Investigation / Diagnostic sampling

Chickenpox is usually a clinical diagnosis. A definitive diagnosis of active VZV infection (chickenpox or shingles) can be made through PCR detection of VZV DNA from a vesicular lesion, which may be useful in immunocompromised or otherwise at-risk children.
- Either a dry swab or swab placed in viral transport medium is suitable
Swabs placed in charcoal transport medium or gel are not suitable for PCR and will not be processed.
- Swab samples should be collected from the base of a de-roofed vesicular lesion.
VZV serology can be used to aid in determination of pre-existing immunity (IgG) or acute VZV infection (IgM)
- The urgent determination of maternal immunity to VZV through IgG testing is central to management of neonates exposed to VZV postnatally.

Management of VZV cases

Most cases of chickenpox and shingles in immunocompetent children require symptomatic treatment only.
Antiviral therapy may be required to treat neonates less than 7 days of age, immunocompromised patients and those with complications of VZV infection.
- Refer to the ChAMP Aciclovir monograph or the ChAMP Valaciclovir monograph for guidance on dosing of both intravenous and oral formulations in the treatment of VZV infection.
- For patients with severe chickenpox, moderate to severe immunosuppression and/or the inability to tolerate oral medications, IV aciclovir may be required initially with the switch made to oral valaciclovir or aciclovir once clinical improvement has been noted.
Zoster immunoglobulin (ZIG) should not be used to treat established VZV infection. ZIG is used as prophylaxis for high-risk individuals following an exposure.

Nursing and infection control considerations

If hospitalisation is needed, strict isolation under airborne precautions is critical due to the high infectivity of VZV.
Transfer to a negative pressure room from triage, if VZV infection is suspected.
Exposed non-immune family members may be infectious from 8-21 days after their first contact with the patient with Chickenpox during their infectious period. Where possible, they should avoid being within the hospital during this period. If this is not possible, discuss options with Infection Prevention and Control.
Implement airborne transmission-based precautions (refer to the Transmissible Diseases Index (internal WA Health only) for further information)
Refer to ED guidelines Rash Management.
Children with chickenpox are infectious from 2 days before the appearance of rash until the vesicles are crusted over. They must be excluded from school / kindergarten / daycare until all lesions are crusted.

Complications

The most common complication is secondary staphylococcal or streptococcal infection of lesions resulting from the child scratching the itchy rash. Infected lesions should be swabbed for bacterial culture (M, C&S) with directed antibiotic therapy given based on culture results. If the patient is known to be MRSA colonised, empiric therapy with an antibiotic with activity against MRSA should be considered.

Severe complications are rare in immunocompetent children, but include:
- Pneumonia (particularly neonates / adults)
- Hepatitis
- Arthritis
- Thrombocytopenia
- Transverse myelitis
- Encephalitis (1.8 per 10 000)
- Cerebellar ataxia (1 in 4000)

Do not use aspirin as an antipyretic during chickenpox due to the risk of Reye’s syndrome.
Do not use ibuprofen in chickenpox due to the reported increased risk of severe bacterial skin infections, including necrotising fasciitis.

Management of contacts of VZV cases

In the setting of chickenpox or disseminated shingles, VZV is spread by inhalation of infectious droplets and aerosols or through direct contact with vesicle fluid or respiratory secretions.
- For chickenpox, the period of infectivity lasts from 2 days before the appearance of the rash until the last crop of vesicles have all crusted.
Patients with localised shingles are much less infectious than patients with chickenpox, with direct contact with vesicle fluid generally required for transmission of infection. In the healthcare environment, lesions should be covered where practicable.
Significant exposure to VZV is defined as:
- Living in the same household as a person with active chickenpox or shingles
- Face-to-face contact without appropriate PPE for at least 5 minutes with a person with chickenpox or exposed facial shingles lesions
- Being in the same room / airspace as a person with chickenpox or exposed shingles lesions for at least one hour
- Direct contact with vesicle fluid from a patient with chickenpox or shingles.
Please notify PCH Infection Prevention and Control if a significant VZV exposure is detected as there are implications for placement and isolation of the exposed patient during hospital visits and admissions in the next 21-28 days.

Vaccination for post-exposure prophylaxis

Vaccination may be effective in preventing infection if given within 5 days of exposure (preferably within 3 days) in immunocompetent hosts older than 12 months.
VZV-containing vaccines should not be given to infants less than 12 months of age.
Varicella-containing vaccines are contraindicated for immunosuppressed patients as they are live vaccines.

Zoster Immunoglobulin (ZIG)

ZIG is available for the prevention of varicella in high-risk patients exposed to VZV. High-risk patients are defined as:
- Neonates < 1 month of age, if their mother is VZV seronegative.
- Premature infants (born less than 28/40 gestation or birthweight less than 1000 g) exposed in hospital, regardless of maternal VZV serostatus.
- Immunocompromised patients
- Pregnant women (VZV seronegative)
ZIG should be administered within 96 hours of exposure but there may be some efficacy if administered up to 10 days post exposure.
The intention to use ZIG should be discussed with the on-call Infectious Diseases specialist.
If an immunosuppressed patient has recent evidence of detectable VZV antibodies, they do not require ZIG.
In the setting of neonatal exposure, ZIG does not generally offer any additional protection if maternal VZV seropositivity is confirmed given the passive acquisition of VZV IgG antibodies in utero.
Written consent is required as Zoster Immunoglobulin is manufactured from pooled human plasma.
Zoster Immunoglobulin - Transfusion Medicine Manual (internal WA Health only) (200 international units / 2mL) can be obtained from Transfusion Medicine. ZIG is administered by slow deep intramuscular injection.
If a person has a second exposure to VZV > 3 weeks after the first dose of ZIG, the dose can be repeated.

Table 1: Zoster immunoglobin weight-based dosing

Weight of patient (kg)	Dose (international units)
0 - 10 kg	200
11-30 kg	400
> 30 kg	600

Table, Zoster immunoglobin based on weight - Immunisation Handbook

Approach to management of VZV exposure in neonates

Neonates exposed to VZV within the first month of life are at high risk for severe disease. Neonatal mortality without intervention is reported to be as high as 30%.

Table 2: Neonatal management based on timing of exposure and maternal immunity to VZV

Timing of Neonatal VZV exposure	Maternal VZV immunity (IgG)	Neonatal management
Primary VZV infection (chickenpox) in mother from 7 days before to 2 days after delivery	N/A – Non-immune by definition	ZIG as soon as possible
Postnatal exposure within first month of life	Mother seronegative (IgG negative) – Non-immune	ZIG as soon as possible
Postnatal exposure within first month of life	Mother seropositive (IgG positive) – Immune	Observe Medical review recommended if chickenpox develops in baby
Premature infants < 28/40 gestation or birthweight < 1000g exposed to VZV before reaching one month corrected age	N/A	ZIG as soon as possible

Prevention

Vaccination with live attenuated Varicella-Zoster vaccine (Varilrix^® or Varivax Refrigerated^®) has few side effects and is recommended for children over 12 months and non-immune adults.
All children less than 14 years of age are recommended to receive 2 doses of varicella-containing vaccine, with the first dose at 18 months of age.
Two doses of varicella-containing vaccine provide more protection and minimise the risk of breakthrough varicella infection in children less than 14 years of age. However, a second dose of varicella-containing vaccine is not covered under the current National Immunisation Program.
Older children ≥14 years and seronegative adults require 2 doses of a varicella-containing vaccine at a minimum interval of 4 weeks to achieve adequate protection from varicella.
A quadrivalent measles-mumps-rubella-varicella (MMRV) vaccine is also available. MMRV vaccine is not recommended as the first dose of MMR-containing vaccine in children less than 4 years of age due to the small but increased risk of fever and febrile seizures.
It is strongly recommended that non-immune household contacts of an immunosuppressed person be vaccinated against varicella.

References

Australian Technical Advisory Group on Immunisation (ATAGI). Australian Immunisation Handbook, Australian Government Department of Health & Aged Care, Canberra, 2024, immunisationhandbook.health.gov.au
Palasanthiran P, Starr M, Jones C, Giles M (eds.). Management of Perinatal Infections, third edition. Australasian Society for Infectious Diseases (ASID), Sydney NSW, 2022.
Mikaeloff Y, Kezouh A, Suissa S, Nonsteroidal anti-inflammatory drug use and the risk of severe skin and soft tissue complications in patients with varicella or zoster disease. British Journal Clinical Pharmacology 2008 Feb;65(2):203-9.
Sone K, Tackley E, Weir S, BET 2: NSAIs and chickenpox, BMJ Emergency Medicine Journal, 2018;35:66-68.

Endorsed by:	CAHS Drug and Therapeutic Committee	Date:	Mar 2026
		Review date:	Jan 2029

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