Chickenpox

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Chickenpox, also known as Varicella, is a highly infectious illness

  • caused by the Varicella Zoster Virus, of the Herpes Virus Family.


Most children catch the disease during the early childhood (2-8 years) and it is most prevalent between March and May.


Chickenpox usually only occurs once due to development of immunity, though reactivation of varicella zoster virus can occur (Shingles).

  • A characteristic vesicular rash and pruritis are common presenting symptoms


People who should seek early medical assessment when exposed / infected (see below):

  • Pregnant women
  • Immunocompromised patients
  • Neonate (<4 weeks of age)
  • Unusual symptoms, chest pain or respiratory difficulty


Aetiology

  • Spread: Infection is spread via airborn particles of saliva and mucous.


  • Incubation Period = 10 - 21 days


  • Infectivity Period = 2 days prior to approximately 5 days after development of the rash.
    • children are considered infectious until all vesicles have crusted over


Shinges (reactivation)

    • Following infection, Varicella Zoster Virus (VZV) remains dormant in the dorsal root ganglia of the sensory nerve fibres entering the spinal cord. Reactivation typically occurs at times of stress or weakened immunity and exhibits initially as pain and then a rash in a dermatomal distribution of the nerve root it has reactivated from.


Clinical features

  • Flu-like symptoms (tend to be worse in adults cf. children)
    • nausea
    • fever
    • aching
    • myalgia
    • headache
    • generally malaise
    • loss of appetite.


  • Rash - develops soon after systemic symptoms
    • usually appears in crops
    • Initially small, itchy papules
    • Vesicles develop after approximately 12 hours - intensely itchy
      • can form on palms and soles
      • crust from days 1-4, which then falls off naturally.


Investigations

Investigation is not normally required.

  • The rash and symptoms are usually characteristic and the diagnosis is clincal.


Management

Management in healthy individuals is symptomatic only.

  • NB: see "Special Circumstances" below.
  • Aciclovir may be considered in adults, particularly if severe infection.
    • Not usually given to healthy children.


Pain / Fever: analgesics and anti-pyretics


Fluids: ensure good fluid intake


Pruritis / Scratching

  • Trim fingernails / cover hands with socks
    • Preventing scratching will minimise risk of skin scarring
  • Calamine Lotion applied to the skin can be soothing
  • Chlorpheniramine may be helpful (>1 year age)


Containment

Patients are considered infectious until the last vesicle has crusted,usually by 5-7 days.

  • Nurseries should be informed, as well as any contacts who fall in the 'high risk' categories discussed below.
  • Travel on aeroplanes will probably not be allowed during the infectious period.
  • Bedding and toys should be kept clean / sterilised.


Morbidity and Mortality

Complications in children are unusual. Adults can be more severely affected.


Bacterial Skin infection can occur on top of the rash


Varicella pneumonitis - 5-15% of adults may develop this and require hospitalisation


Congenital Varicella infection - see below


Varicella Meningitis


Prevention

Varicella Vaccination is available, though not currently offered under the routine NHS Childhood Immunisation Schedule (UK).


Special Circumstances

Pregnant Women

90% of pregnant women will be immune to Chickenpox due to previous infection

  • Shingles will not affect the pregnancy
  • Chickenpox occurs in 3 in 1000 pregnancies
    • Risk of Congenital Varicella infection
  • Immunity can be assumed if there is a clear history of previous chickenpox and the mother may be reassured.


Exposed pregnant women who are uncertain of their immunity should present for serological testing for varicella IgG (suggesting immunity) and IgM (suggesting recent infection).

  • Assess certainty and level of exposure
  • Establish the gestation of pregnancy
  • Serological testing
  • Seek specialist advice re. need for Varicella Zoster Immunoglobuline (VZIG) prophylaxis
  • couselling on the risk of congenital varicella should be offered
  • consider antiviral treatment
  • consider follow-up and need for repeat serology


Infected Pregnant Women

  • Seek specialist obstetric / foetal medicine advice re. diagnostic tests, counselling re. congenital varicella, anti-viral treatment and follow-up.
  • Give symptomatic treatment also
  • Admit to hospital if severe or unusual symptoms
    • ideally with obstetric, infectious disease and paediatric support available


Exposure of a Neonate

Varicella Zoster Immunoglobulin (VZIG) is usually recommended for infants where:

  • mother develops chickenpox in the period 7 days before to 7 days after delivery
    • antibody testing not required first
      • premature, low birth weight babies, or those who have had many blood tests and transfusions may not have (sufficient) maternal antibody to VZV. These babies should have serological testing following exposure.
    • Neonates born more than 7 days after maternal chickenpox eruption are not usually a concern since the baby will have maternal antibodies
    • Maternal Zoster infection (Shingles) is not usually a concern, since the baby will have the maternal antibodies.
  • Neonate is exposed to chickenpox or herpes zoster (other than the mother) in the first 7 days and is VZ antibody negative
  • Infant of any age exposed to chickenpox or herpes zoster and still requiring intensive / prolonged special care and is VZ antibody negative.


Infection

Approximately half of neonates exposed to maternal varicella will become infected despite VZIG prophylaxis.

  • early treatment with IV aciclovir is recommended since infection may rarely be fatal.


Exposure of a Breast-feeding mother

  • Symptomatic treatment
  • Consider aciclovir if <24hrs since onset, severe chickenpox or risk of complications
  • Seek advice re. continuation of breastfeeding
  • Provide contact advice and when to see further medical advice
  • Admit if complications suspected

Exposure of Immunocompromised patients

  • Seek immediate specialist advice re. confirming the diagnosis and whether urgent antiviral treatment is required.
  • symptomatic treatment.
  • Give advice about contact with other people and when to seek medical advice.
  • Admit to hospital if serious complications suspected.


Exposure in a non-immune immunocompromised patient requires prophylactic aciclovir or zoster immunoglobulin.


Active infection in immunocompromised patients should be treated aggressively with IV aciclovir.


Exposure of Healthcare Workers

Vaccinated or definite history of chickenpox

  • continue working, but contact occupational health if unwell or develop a rash.


Negative or uncertain history of chickenpox Test to determine immunity and advise that the person may develop chickenpox.

  • Avoid contact with high-risk patients for 8–21 days after contact with chickenpox
  • contact occupational health if unwell or develop a rash.
  • offer varicella vaccine to reduce the risk of exposing patients to the varicella zoster virus in the future.

Shingles

Shingles is caused by re-activation of latent VZV.


A prodrome of tingling or pain often preceeds the painful vesicular eruption that occurs within a dermatomal distribution. As with Chickenpox, the blisters occur in crops and may become pusular before crusting over.


Treatment

  • analgesia
  • oral aciclovir may shorten the attack if given early
  • High dose IV aciclovir is required for immunosuppressed and high risk patients.
  • antibiotics if secondary bacterial infection occurs,


Complications

  • Post-herpetic neuralgia (persistent pain)
  • Ocular disease (consider when the opthalmic division of CN V is affected)
  • Motor Neuropathy (rare)

References


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