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.

Read the full PCH Emergency Department disclaimer.

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, chickenpox is generally a benign and self-limiting illness.
Hospitalisation is rarely required in uncomplicated chickenpox.
If hospitalisation is needed, strict isolation under airborne precautions is critical due to its high infectivity.
Neonates and immunocompromised children have a high risk of severe varicella infection and disseminated disease.
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.

General

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 who received Zoster Immunoglobulin (ZIG).
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.
Shingles is relatively uncommon in children, but is more common if the original infection occurred in the first year of life.
Varicella zoster (Chickenpox, Shingles and unspecified) is a notifiable disease under the Public Health Act 2016.

Risk factors

Patients at risk of severe primary disease:

Adults and adolescents over 15 years of age
Pregnant women
Neonates
Immunocompromised children and adults.

Assessment

Chicken pox 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 vesicular lesions appear, more concentrated over the trunk than the limbs.

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.
Any significant changes should be reported immediately to the medical team.

Investigation/Diagnostic sampling

A definitive diagnosis of active VZV infection (chickenpox or shingles) can be made through PCR detection of VZV DNA from a vesicular lesion.
- 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)
VZV PCR from a swab sample is preferred for diagnosis of active infection.
The urgent determination of maternal immunity to VZV through IgG testing is central to management of neonates exposed to VZV postnatally.

Management

Most cases require symptomatic treatment only.
Antiviral therapy may be required to treat neonates, immunocompromised patients and those with severe VZV infection.
- Refer to the Aciclovir monograph - ChAMP (PDF) or the Valaciclovir monograph - ChAMP (PDF) for guidance on dosing of both intravenous and oral formulations in the treatment of VZV infection.
Shingles in immunocompetent children does not usually need treatment.
Zoster immunoglobulin (ZIG) should not be used to treat established VZV infection.

Nursing and infection control considerations

Isolate to a negative pressure room, from triage, if lesions are not fully dried or crusted.
Non immune family members may be infectious from 8-21 days after contact with infected person.
Implement standard + contact + airborne isolation precautions (refer to the Transmissible Diseases Index (internal WA Health only) for further information)
Refer to Rash Management.
Analgesia as required.

Complications

The most common complication is secondary staphylococcal or streptococcal infection of lesions resulting from the child scratching the itchy rash. This can be treated with oral flucloxacillin or cephalexin. If the patient is known to be MRSA colonised consider use of an antibiotic with activity against MRSA.

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)

The administration of aspirin as an antipyretic during chickenpox may result in Reye’s syndrome.
Do not use ibuprofen in chickenpox due to the risk of necrotising fasciitis.^5,6

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, especially where the lesions can be covered.
Significant exposure to VZV is defined as:
- Living in the same household as a person with active chickenpox or shingles
- Face-to-face contact for at least five minutes with a person with chickenpox or exposed shingles lesions
- Being in the same room 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 & 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.

Zoster Immunoglobulin (ZIG)

ZIG is available for the prevention of varicella in high risk patients defined as:
- Infants < 1 month of age
- Immunosuppressed patients
- Pregnant women

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.
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. Phone Transfusion Medicine to request supply, they hold only limited stock and will advise once the requested quantity of ZIG is available. Send the green request form to Transfusion Medicine when the patient is ready for the dose to be administered.
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 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 seronegative adults.
A single dose of varicella-containing vaccine is sufficient for children up to their 14th birthday.
VZV vaccination is currently given at 18 months on the National Immunisation Program schedule.
Older children and seronegative adults require 2 doses of a varicella-containing vaccine at a minimuminterval of 4 weeks.
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

Strauss et al 1988. Accessed at www.uptodate.com.
AMH Children’s Dosing Companion (2021) Australian Medicines Handbook Pty Ltd 2021.
Australian Technical Advisory Group on Immunisation (ATAGI). Australian Immunisation Handbook, Australian Government Department of Health, Canberra 2018. immunisationhandbook.health.gov.au
Palasanthiran P, Starr M, Jones C, Giles M (eds.). Management of Perinatal Infections. Australasian Society for Infectious Diseases, Sydney, 2014.
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. doi: 10.1111/j.1365-2125, [Cited 26 Oct 2021] Available from: https://pubmed.ncbi.nlm.nih.gov/18251759
Sone K, Tackley E, Weir S, BET 2: NSAIs and chickenpox, BMJ Emergency Medicine Journal, 2018;35:66-68, [Cited 26 Oct 2021] Available from: https://emj.bmj.com/content/35/1/66

Endorsed by:	CAHS Drug and Therapeutic Committee	Date:	Oct 2021
		Review date:	Sep 2024

This document can be made available in alternative formats on request for a person with a disability.