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Varicella-zoster infection (chickenpox and shingles)

Queensland Health Guidelines for Public Health Units

Revision History

Version Date Changes
1.0 June 2008  Full revision of guideline. 
1.1 June 2018 Minor updates

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Infectious Agent

The infectious agent is Varicella zoster virus (human herpesvirus 3).

Notification Criteria

Varicella (chickenpox)

Reporting

Both confirmed cases and probable cases should be notified.

Confirmed case

A confirmed case requires either:

  1. Laboratory definitive evidence AND clinical evidence
    OR
  2. Clinical evidence AND epidemiological evidence.

Laboratory definitive evidence

  1. Isolation of varicella-zoster virus from a skin or lesion swab. If the case received varicella vaccine between 5 and 42 days prior to the onset of rash the virus must be confirmed to be a wild type strain
    OR
  2. Detection of varicella-zoster virus from a skin or lesion swab by nucleic acid testing. If the case received varicella vaccine between 5 and 42 days prior to the onset of rash the virus must be confirmed to be a wild type strain
    OR
  3. Detection of varicella-zoster virus antigen from a skin or lesion swab by direct fluorescent antibody. If the case received varicella vaccine between 5 and 42 days prior to the onset of rash the virus must be confirmed to be a wild type strain
    OR
  4. IgG seroconversion or a significant increase in antibody level, such as a fourfold or greater rise in titre to varicella-zoster virus (VZV) EXCEPT if the case has received a VZV-containing vaccine 8 days to 8 weeks prior to convalescent specimen collection. (NOTE: paired sera must be tested in parallel)

Clinical evidence
Acute onset of a diffuse maculopapular rash developing into vesicles within 24 – 48 hours and forming crusts (or crusting over) within 5 days.

Epidemiological evidence
An epidemiological link is established when there is:

  1. Contact between two people involving a plausible mode of transmission at a time when:
    a.  one of them is likely to be infectious
    AND
    b.  the other has illness 10 – 21 days after contact
    AND
  2. At least 1 case in the chain of epidemiologically-linked cases is laboratory confirmed.

Probable case
A probable case requires clinical evidence only.

Note: Laboratory confirmation should be strongly encouraged for vaccinated cases. If positive, samples should be referred for identification as a vaccine or wild type strain.

Zoster (shingles)

Reporting

Both confirmed cases and probable cases should be notified.

Confirmed case

A confirmed case requires laboratory evidence AND clinical evidence.

Laboratory definitive evidence

  1. Isolation of varicella-zoster virus from a skin or lesion swab
    OR
  2. Detection of varicella-zoster virus from a skin or lesion swab by nucleic acid testing
    OR
  3. Detection of varicella-zoster virus antigen from a skin or lesion swab by direct fluorescent antibody.

Clinical evidence
A vesicular skin rash with a dermatomal distribution that may be associated with pain in skin areas supplied by sensory nerves of the dorsal root ganglia.

Probable case
A probable case requires clinical evidence only.

Note: Laboratory confirmation should be strongly encouraged for vaccinated cases. If positive, samples should be referred for identification as a vaccine or wild type strain.

Varicella-zoster infection - (not elsewhere classified)

Reporting

Only confirmed cases should be notified.

Confirmed case
A confirmed case requires laboratory definitive evidence, either in the absence of clinical information or where clinical evidence does not meet criteria for varicella-zoster infection (chickenpox) or varicella-zoster infection (shingles).

Laboratory definitive evidence

  1. Isolation of varicella-zoster virus
    OR
  2. Detection of varicella-zoster virus by nucleic acid testing
    OR
  3. Detection of varicella-zoster virus antigen by direct fluorescent antibody
    OR
  4. IgG seroconversion or a significant increase in antibody level, such as a fourfold or greater rise in titre to varicella-zoster virus (VZV) EXCEPT if the case has received a VZV-containing vaccine 8 days to 8 weeks prior to convalescent specimen collection. (NOTE: paired sera must be tested in parallel).

Notification Procedure

Pathology Laboratories:
To notify on microbiological or serological confirmation by usual means.

Reporting to NOCS

Only confirmed cases should be notified.

Public Health Significance and Occurrence

In healthy children, chickenpox is usually a mild disease of short duration. However, complications occur in approximately 1% of cases. It is more severe in adults and can cause serious and even fatal illness in immunosuppressed subjects of any age.

Congenital varicella syndrome has been reported after varicella infection in the first and second trimesters of pregnancy and may result in foetal skin scarring, limb defects, ocular anomalies and neurologic malformations. There is a higher risk to the foetus when maternal infection occurs in the second trimester compared with infection in the first trimester (1.4% vs 0.55%).

The 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 – 30% of their newborn infants.

Before the universal varicella vaccination program commenced in Australia in 2005, there were about 240,000 cases, 1,500 hospitalisations and 7 – 8 deaths each year from varicella. The highest rates of hospitalisation occur in children less than 4 years of age.  Incidence rates are likely to decline in Australia, as has occurred in the USA where universal varicella vaccination since 1995 has resulted in reductions in disease and hospitalisation rates of greater than 80%.

Shingles is a localised vesicular rash resulting from reactivation of latent varicella zoster virus in a period of waning immunity. It is often a serious illness in older adults and immunocompromised individuals. Shingles is uncommon before the age of 12 years, and most cases occur over the age of 50 years.

Clinical Features

Chickenpox is an acute generalised viral disease with sudden onset of slight fever, mild constitutional symptoms and a skin eruption that is maculopapular for a few hours, vesicular for 3 – 4 days and leaves a granular scab. The lesions are present in a variety of stages at the same time. Mild, atypical and inapparent infections may occur. Secondary bacterial infections of the vesicles may leave disfiguring scars or result in necrotising fasciitis or septicaemia.

Zoster is a local manifestation restricted to skin areas supplied by sensory nerves of a single or associated group of dorsal root ganglia. Severe pain and paraesthesia is common. Post-herpetic neuralgia can occur.

Reservoir

Humans.

Mode of Transmission

  • From chickenpox cases: airborne; droplets; direct contact with nasopharyngeal secretions or lesions of an infected person.
  • From shingles cases: direct contact with lesions.

Incubation Period

14 – 16 days on average (range 10 – 21 days).

Period of Communicability

For chickenpox, the infectious period is as long as 5, but usually 1 – 2 days before the rash appears and until all the vesicles have formed scabs, usually within 5 days of rash onset. The infectious period for shingles is from rash onset for up to a week. Susceptible individuals should be considered infectious for 10 – 21 days following exposure.

Susceptibility and Resistance

Susceptibility to chickenpox is universal among those not previously infected or vaccinated. Susceptibles have an 80% – 90% risk of infection after household exposure to varicella.

Infection usually confers long immunity; second attacks are rare in immunocompetent people.

If a vaccinated person does get 'breakthrough varicella', it is usually a mild case. However, breakthrough varicella infections are infectious.

Management

Suspected Cases

  • Investigation
    Rule out varicella vaccine reaction as cause of the rash (a mild rash occurs in 1 – 5% of recipients of varicella vaccine, typically 1 – 3 weeks after vaccination). In consultation with the attending medical practitioner, ascertain any contact with pregnant women or immunocompromised individuals.
  • Restriction
    Chickenpox: Cases should be excluded from childcare, school or work until all the vesicles have dried and crusted – usually by the 5th day of the rash, usually earlier for vaccinated children with breakthrough varicella.
    Shingles: Children should be excluded from childcare or school until all vesicles have dried and crusted. Infection control guidelines for health care workers indicate that if all localised lesions are able to be covered with an appropriate dressing, health care staff may attend work. However, if attendance is likely to result in significant exposure to high risk contacts (see below), or if shingles are disseminated or located in areas unable to be covered, health care staff should be excluded from work until all lesions have dried and crusted.
  • Treatment
    Children with chickenpox should not receive salicylates, because of the risk of Reye's syndrome.
    Antivirals are generally not recommended in healthy children with chickenpox.
  • Counselling
    The patient should be advised of the nature of the infection and its mode of transmission.

Contacts

  • Definition
    High risk contacts include:
    - pregnant women who are, or are presumed to be, susceptible
    - neonates whose mothers develop varicella between 7 days prior to and 1 month after delivery
    - neonates exposed to varicella (other than from their mother) in the first month of life, if their mother is seronegative
    - premature infants (born less than 28 weeks gestation or birthweight less than 1000g) exposed in hospital, regardless of maternal history of varicella
    - immunocompromised individuals, particularly if known to lack detectable antibodies to varicella

    Significant exposure for these contacts is defined as living in the same household as a person with active chickenpox or shingles, or direct face-to-face contact with a person with chickenpox or shingles for at least 5 minutes, or being in the same room for at least one hour.  In the case of varicella infection, the period of infectivity is from 48 hours before the onset of rash until crusting of all lesions has occurred.

Management:
Zoster immunoglobulin (ZIG) must be given, as early as possible, intramuscularly to neonates whose mothers develop varicella between 7 days prior to and 2 days after delivery, as neonatal mortality without ZIG is 30% in this setting. 

Other high risk contacts should be given ZIG intramuscularly within 96 hours of significant exposure to either chickenpox or shingles. Immunocompetent high risk contacts (other than neonates) should be tested for antibodies if practicable, as long as this does not delay ZIG administration for greater than 96 hours from their first significant exposure. 

For immunocompromised individuals, ZIG can be given up to 10 days after exposure although within 96 hours is preferable. Immunocompromised contacts with recent evidence of detectable antibodies do not require ZIG, unless they have a history of transfusion or receiving intravenous immunoglobulin in the previous 3 months.

Normal human immunoglobulin can be used for the prevention of chickenpox if ZIG is unavailable. The dose of ZIG is as follows:

Weight of Patient (kg)Dose (IU)
 0 - 10  200
 11 - 30  400
 Over 30  600

ZIG can be ordered from the local Red Cross Blood Bank by consulting with the medical officer on 07 3838 9233 or 07 3838 9010. Transportation of ZIG to a general practice surgery may have to be arranged through a private pathology company.

Should the time since initial exposure have exceeded 96 hours, high-risk contacts should be referred to their clinical specialist who may consider the use of acyclovir for prophylaxis.

  • Counselling:
    Provide information on the nature of the infection and its mode of transmission.

    Provide plain language explanation of the potential outcomes of chickenpox in high risk contacts and the risks and benefits of ZIG.
    (NB While ZIG may prevent or modify the course of chickenpox in pregnancy, it may not abolish the risk of foetal infection.  Pregnant women given ZIG should be referred to their obstetrician).

Preventive Measures

It is recommended that at least one dose of a varicella-containing vaccine be given to all non-immune children from the 2nd year of life up to 13 years of age.

The National Immunisation Program Schedule provides a combined measles, mumps, rubella and varicella (MMRV) vaccine free of charge to all children aged 18 months. Prior chicken pox infection is not a contraindication to this vaccine, and such children should still receive MMRV vaccine.

While current evidence indicates that 2 doses of varicella-containing vaccine increases protection and minimises the risk of breakthrough varicella, routine administration of 2 doses for children up to 13 years of age is not included on the NIP schedule at this time.

Vaccination is recommended for all people aged 14 years and older without a reliable history of chickenpox, either by confident clinical diagnosis or serological testing. Adolescents aged from 14 years to under 20 years who have not previously received any varicella vaccines are now eligible for 2 funded vaccines. Two doses of vaccine at least 4 weeks apart are required. It is particularly recommended that susceptible individuals in the following categories be vaccinated: those in high-risk occupations (child care, health care, teachers); women prior to pregnancy or immediately after delivery; parents of young children; household contacts of immunosuppressed people.

The vaccine has been shown to be generally effective in preventing varicella infection following exposure when given within 3 and up to 5 days. However, ZIG rather than vaccine should be given to high risk contacts as specified under Contact Management. Vaccine is not recommended by the NHMRC before the age of 12 months.

Feedback

Report to notifying agency.

Summary

Provide Communicable Diseases Branch, Queensland Health with a report upon request.

References

Heymann, D. (Ed). 2004. Control of Communicable Diseases Manual, 18th edition. American Public Health Association: Washington.

National Health and Medical Research Council 2008.  9th Edition Australian Immunisation Handbook.  Canberra: National Capital Printing.

Last updated: 5 June 2018