Chickenpox and shingles (varicella / herpes zoster)

Notification requirement for chickenpox or shingles

Varicella is a ‘routine’ notifiable condition and must be notified by medical practitioners and pathology services in writing within 5 days of diagnosis.

This is a Victorian statutory requirement.

Primary school and children’s services centre exclusion for chickenpox or shingles

Primary school and children’s services centre exclusion differs according to case or contact status:

• Cases should be excluded until all blisters have dried. This is usually at least 5 days after the rash appears in unimmunised children, but may be less in previously immunised children.
• Any child with an immune deficiency or receiving chemotherapy should be excluded for their own protection. Otherwise, contacts are not excluded.

Infectious agent of chickenpox or shingles

The causative agent is called human herpesvirus 3 (HHV-3) or varicella zoster virus (VZV).

Identification of chickenpox or shingles

Clinical features

Varicella (chickenpox)

Chickenpox typically presents with:

• low-grade fever
• malaise
• rash that progresses from maculopapular to vesicular (blistered) to crusted lesions over about 5 days

Lesions appear in three or four crops, primarily on the trunk, and to a lesser extent on the face, scalp, limbs and mucous membranes of the mouth. Some cases (about 5 per cent) are subclinical or exceedingly mild in nature.

Adults tend to experience more severe disease than children. Rarely, the disease may be fatal.

As vaccination rates have increased, an increasing number of varicella cases now occur among vaccinated persons (breakthrough cases). These cases are generally much milder, with a lower fever and more rapid recovery.

Vaccinated cases often have fewer than 50 rash lesions and fewer vesicles compared with 300 or more lesions and many vesicles in unvaccinated persons.

Complications can include:

• secondary bacterial infection of the skin lesions
• primary varicella pneumonia
• aseptic meningitis
• encephalitis
• Reye syndrome (acute encephalopathy with fatty infiltration and dysfunction of the liver).

Newborns and immunosuppressed patients are at greatly increased risk of severe chickenpox.

Herpes zoster (shingles)

VZV remains in a latent state in human nerve tissue and reactivates in about 30 per cent of infected persons during their lifetime, resulting in herpes zoster (shingles). Herpes zoster or shingles is characterised by:

• a predominantly unilateral vesicular eruption within a dermatome
• severe pain that may precede lesions by 48–72 hours
• a rash that can last several weeks, depending on severity. The rash is often more widespread and persistent in immunosuppressed patients.

Patients must be carefully evaluated to ensure that there is no eye or auditory nerve involvement when the rash involves the ophthalmic area of the face. Specialist treatment is mandatory in this case, because blindness, hearing impairment or other complications can result.

Incidence increases with age, and children under 12 years are rarely affected unless immunosuppressed or initially infected as infants.

Disseminated herpes zoster is a form of shingles characterised by skin lesions outside the affected dermatome, with potential involvement of other organs (for example, causing hepatitis or encephalitis).

A debilitating complication of herpes zoster in many (especially elderly) patients is prolonged pain (post-herpetic neuralgia) that may persist for months after resolution of the skin lesions.

Diagnosis

Confirmation of the diagnosis is generally only required when the clinical picture is atypical. It is made by one of the following:

• isolation of the virus in cell cultures
• visualisation by electron microscopy
• serological tests for antibodies
• immunofluorescence on a lesion swab or fluid
• nucleic acid testing or polymerase chain reaction (PCR) on a lesion swab or fluid.

Incubation period of varicella zoster virus

The incubation period is 2–3 weeks and is usually 14–16 days. This may be prolonged in immunosuppressed persons or following immunoglobulin administration as passive immunisation against varicella.

Reservoir of varicella zoster virus

Humans are the reservoir.

Mode of transmission of varicella zoster virus

Chickenpox transmission is mainly person-to-person by airborne respiratory droplets, but also occurs by direct contact with vesicle fluid of chickenpox cases or contact with the vesicle fluid of patients with herpes zoster. Immunosuppressed cases with disseminated herpes zoster may also transmit via respiratory droplets. Indirect contact occurs through articles freshly soiled by discharges from vesicles of infected persons. Scabs are not infective.

Period of communicability of chickenpox or shingles

It is usually communicable for 1–2 days before the onset of the rash, continuing until all the lesions are crusted. Communicability may be prolonged in patients with altered immunity.

People with zoster are considered infectious for a week after lesions appear, when they are moist.

Susceptibility and resistance to chickenpox or shingles

Chickenpox is highly infectious, shingles much less so. More than 80 per cent of non-immune household contacts of a case of chickenpox will become infected. Non-immune people exposed to shingles cases will develop chickenpox (not zoster) if they become infected.

Second attacks of chickenpox are rare but do occur.

Infection remains latent in some individuals and can recur years later as shingles.

Patients who are at high risk of severe disease/complications if they do not have immunity include:

• infants less than 1 month old
• pregnant women
• immunosuppressed individuals, including those with haematological malignancies, those on chemotherapy or high-dose steroids, or those with HIV infection.

Public health significance and occurrence of chickenpox or shingles

Chickenpox is a highly contagious but generally mild disease and is endemic in the population. It becomes epidemic among susceptible individuals mainly during winter and early spring. More than 90 per cent of cases are children under 15 years of age.

Herpes zoster (shingles) occurs due to the reactivation of latent virus from the dorsal root ganglia. About 1 in 3 people will get shingles in their lifetime. Shingles usually affects older people, and the risk of complications increases with age, particularly for: those over the age of 65, Aboriginal and Torres Strait Islander people aged 50 and over and some people with weakened immune systems.

Control measures for chickenpox or shingles

Preventive measures

Varicella (chickenpox) vaccine

Varicella-containing vaccine is recommended for:

• children aged 12 months to 14 years
• adolescents aged 14 years and over and adults who have not received 2 doses of varicella-containing vaccine, particularly
  • healthcare workers
  • childhood educators and carers
  • people who work in long-term care facilities

A single dose of varicella-containing vaccine is 80-85% effective in preventing chickenpox and very effective against severe disease.

Immunisation against chickenpox is provided free of charge to eligible people under the National Immunisation Program Schedule for:

• Children at 18 months – immunisation against chickenpox is given as a combined vaccine containing protection against measles, mumps, rubella and varicella (MMRV). Children who have had chickenpox should still receive the combination vaccine.
• Young people up to and including 19 years – free catch-up varicella vaccines are available for all young people who have not completed the recommended schedule.
• Refugees and humanitarian entrants aged 20 years and over.

Live attenuated varicella vaccine (VV) is also available as a monovalent vaccine.

Vaccination with varicella vaccine is contraindicated in immunocompromised people and pregnant women. For further details, see the current edition of the Australian Immunisation Handbook.

Zoster (herpes zoster) vaccine

Herpes zoster, commonly known as shingles, is the disease caused when the chickenpox virus reactivates.

Zoster vaccines are recommended for:

• people aged 50 years and over who are immunocompetent
• people aged 18 years and over who are immunocompromised
• people aged 50 years and over who are household contacts of a person who is immunocompromised.

Zoster vaccine is provided free of charge under the National Immunisation Program Schedule for:

• people aged 65 years and over
• Aboriginal and Torres Strait Islander people aged 50 years and over
• immunocompromised people aged 18 years and over considered at increased risk of herpes zoster, due to an underlying condition and/or immunomodulatory/immunosuppressive treatments.
• For further details, refer to the National Immunisation Program – Shingles vaccination and the current edition of the Australian Immunisation Handbook | Zoster.

Control of case

Varicella (chickenpox)

In the nonhospitalised patient with a normal immune system and uncomplicated varicella, aciclovir is not recommended because it provides only marginal benefits. In immunocompromised patients and in normal patients with severe disease or with complications of varicella (such as pneumonitis, hepatitis or encephalitis) aciclovir may be used. Consult the current version of Therapeutic guidelines: antibiotic

General measures include:

• tepid bathing or cool compresses, which may help to alleviate itching
• exclusion from school until all blisters have dried, or at least for 5 days after eruption first appears. Some remaining dry scabs are not a reason for continued exclusion
• advising adults to stay away from work for at least 5 days
• avoiding contact with high-risk susceptible persons.

Aspirin should never be given to children under 16 years of age with varicella, due to a strong association with the development of Reye syndrome.

Inpatients diagnosed with varicella need to be managed in a negative pressure room with contact and airborne precautions.

Herpes zoster (shingles)

Some antiviral medications (famciclovir, valaciclovir or aciclovir) have been effective in treating varicella zoster infections in patients with a rash less than 72 hours old. These medications provide pain relief, accelerated healing and may help reduce the incidence of postherpetic neuralgia.

More intensive treatment is warranted in high-risk patients. Consultation with an infectious diseases physician is advised. Adequate analgesia should be provided.

Inpatients diagnosed with disseminated shingles need to be managed in a negative pressure room with contact and airborne precautions. A patient with non-disseminated shingles should also be in a single room with contact precautions if blisters are not able to be covered.

Control of contacts

Significant contact is defined as face-to-face contact for at least 5 minutes, being in the same room for greater than 1 hour or household contact.

Any non-immune person admitted to hospital who has a known exposure to varicella should be isolated for days 10–21 after exposure or up to 28 days if given zoster immunoglobulin (ZIG), to reduce the risk of spread to immunosuppressed patients.

Post-exposure prophylaxis for contacts

Varicella vaccination

Vaccination may be used to prevent or attenuate illness if given to susceptible contacts within 5 days (preferably 72 hours) of first exposure. If varicella vaccine is not contraindicated, it can be offered to non-immune age-eligible children and adults who have had a significant exposure to varicella or herpes zoster and want protection against primary infection with varicella.

Vaccination with varicella vaccine is contraindicated in immunocompromised people and pregnant women.

For further details, see the current edition of the Australian Immunisation Handbook.

Zoster immunoglobulin (ZIG)

ZIG prevents or modifies severity of varicella in people at high risk who report a significant exposure to varicella or herpes zoster. High-risk susceptible contacts where vaccination is not indicated, includes neonates, pregnant women and immunosuppressed persons. This cohort should be offered ZIG, preferable within 96 hours and up to 10 days after exposure. The Australian Red Cross Blood Service provides restricted amounts of high-titre ZIG. If vaccination is not contraindicated, it should follow at least 5 months later.

For further details, see the current edition of the Australian Immunisation Handbook.

Outbreak measures for chickenpox or shingles

Timely vaccination of susceptible contacts is indicated to contain an outbreak.

Special cohorts

Immunosuppressed and their household contacts

Immunosuppressed people, particularly those with primary or acquired diseases associated with cellular immune deficiency, and people receiving immunosuppressive therapy, are at high risk of more severe infection. ZIG should be offered to these patients if exposed. Susceptible household contacts of these patients should be vaccinated.

Pregnancy

Varicella infection during the first trimester of pregnancy carries a small risk of miscarriage. Maternal infection before 20 weeks rarely may result in the foetal varicella zoster syndrome, with the highest risk (2 per cent) occurring at 13–20 weeks. Clinical manifestations include growth retardation, cutaneous scarring, limb hypoplasia and cortical atrophy of the brain.

Intrauterine infection can also result in herpes zoster in infancy. This occurs in less than 2 per cent of infants. The highest risk is associated with infection in late pregnancy. In the third trimester, maternal varicella may precipitate the onset of premature labour. Severe maternal varicella and pneumonia at any stage of pregnancy can cause foetal death.

Where chickenpox develops in pregnancy, specialist medical review within 24 hours of rash onset is indicated to consider treatment options.

Susceptible pregnant women who have been exposed during pregnancy should seek specialist obstetric advice. Susceptibility can be assessed by serological testing for varicella immunoglobin G (IgG). The woman may be offered ZIG and antivirals (famciclovir, valaciclovir or aciclovir), especially where delivery is imminent.

Neonates (less than 1 month old)

Where neonates develop varicella before 10 days of age, or when maternal chickenpox develops within 7 days of delivery and up to 48-hours postpartum, the neonatal fatality rate is up to 30 per cent without treatment. Treatment of mothers and neonates is vital.

Premature babies and infants less than one month old who develop varicella may require specific treatment. Seek expert advice.

Healthcare workers

On commencement at a new workplace, all healthcare workers with an uncertain history of varicella infection should be sero-tested and offered immunisation, if they are susceptible.

If a chickenpox-like rash develops in the 6 weeks after immunisation, the worker should be removed from patient and staff contact until varicella is excluded or lesions have crusted over.

Healthcare workers with chickenpox should not attend work until they are no longer infectious.

If a healthcare worker is exposed to a confirmed case of varicella or herpes zoster they may continue working with other staff patient contact, if they have a history of previous infection or immunisation. They should be advised to report any febrile symptoms or rash developing within 3 weeks of exposure and then avoid contact with other staff patient contact until varicella is confidently excluded.

If the worker is non-immune and has been exposed, vaccination within 5 days of exposure is indicated. They should report any rash that occurs within 6 weeks of vaccination and avoid patient and staff contact, as above. If vaccination is refused, no patient contact should take place between days 8 and 21 after first exposure.

Shingles in a healthcare worker

Workers should not care for high-risk patients until all lesions have crusted over. Other patients can be cared for as long as lesions can be adequately covered.