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Chickenpox - not just a childhood disease

Kirsty Armstrong
SRN FPCert BSc(Hons) NPDip
Senior Lecturer/Practitioner
Faculty of Health and Social Care Sciences
St George's Hospital
Tooting, London and Kingston University
Nurse Practitioner
Ashville Surgery
Fulham
London
E:karmstro@hscs.sghms.ac.uk

Chickenpox (varicella) is a highly infectious disease - transmission is by airborne droplet infection (sneezing) or by personal contact with either varicella or shingles lesions. First contact with the virus will result in chickenpox; however, on second contact the virus (which has lain dormant in the dorsal root ganglia) will result in herpes zoster or shingles. A?person cannot develop chickenpox twice, but if they do not develop shingles on second contact their antibody titre to varicella will rise.
The incidence of chickenpox is on the increase in the under-fives, possibly due to the nature of our expanding social lives and our tendency to socialise more before school years. Between 1983 and 1998 occurrence in children aged 4-10 years doubled, with the spread in the older age groups falling substantially.(1) This means that primary care nurses are more likely to encounter the illness in toddlers and young children than in other age groups.
Chickenpox is endemic in developed countries, and while most cases result only in some scarring, in some individuals, such as the immunocompromised, pregnant women and neonates, it can increase rates of morbidity (long-term damage) or mortality. In the UK varicella has been shown to cause 30 deaths a year, of which one- third are associated with immunosuppression.(2)

Diagnosis
The most obvious symptom of chickenpox is the rash. However, rashes are often difficult to diagnose, and chickenpox can sometimes look like nettle rash, pityriasis rosea or even urticaria. Practice makes perfect, and the more cases you see and diagnose the better you will become at recognising the rash. Take a careful history with attention to details such as history and timing of exposure, any prodromal symptoms (eg, recent cold or grumpiness associated with nonspecific fever), presentation today and what the rash looks like, the season and the age of the child. Armed with this information you should be able to make a diagnosis with which you feel confident.

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Childhood varicella
The incubation period for the chickenpox virus is approximately 21 days, and the child is infectious from 1-2 days before the rash presents until the lesions become dry (ie, stop weeping or containing fluid). You are more likely to see varicella between March and May as the occurrence is seasonal, mostly seen in winter and spring although anecdotally there is some occurrence in the summer months. Children may present with a fever, abdominal pain or nausea, but the most common symptom is the rash, which usually starts on the trunk and then spreads all over the body, and can include the mucous membranes (very uncomfortable in the anogenital area), scalp and limbs. Coverage differs between individuals - some may have only a few spots, while others may be totally covered.
One of the main irritations associated with chicken pox is the itchiness of the rash. As blisters itch and break, scabs form and the blisters may become infected by bacteria (a "secondary" bacterial infection). Avoiding scratching is the best method to avoid secondary infection and, in the long term, scarring. There are a number of ways to soothe this itchiness, including sodium bicarbonate baths or paste applied directly to the lesions, calamine lotion (nonoily), which when kept in the fridge will relieve immediately, or if the itch is severe, chlorpheniramine, used as directed and according to age (not in the under-ones), which is particularly useful at night due to its sedative effect.
There are some rare complications associated with chickenpox, such as pneumonia, meningoencephalitis, acute epiglottitis and leukopenia. Urgent referral to a medical practitioner is advised if the patient is:(3)

  • On steroids or otherwise immunosuppressed.
  • Breathless.
  • Confused or with a severe headache.
  • A baby under four weeks (neonates have a ­mortality of 30%).
  • Pregnant.
  • HIV-positive or has cancer.
  • An elderly person and has shingles.

Fetal varicella syndrome
If infection occurs in the first and second trimesters of pregnancy, fetal varicella syndrome can occur. The resulting effects on the fetus include microcephaly (small brain), hydrocephalus (water on the brain), limb hypoplasia (small limbs), microphthalmia and cataracts causing blindness, scarring and growth retardation. In the first trimester the risk of fetal varicella syndrome is calculated at less than 1%; the critical period arises between 13 and 20 weeks when risk is calculated at 2%.(2) If you have a pregnant mother presenting with a history of chickenpox contact, check the history carefully. If you or your colleagues are concerned, take a sample and send for same-day assay of antivaricella-zoster antibodies to your nearest PHLS (Public Health Laboratory Service) centre (see Resources section). If the mother has no antibodies the PHLS will advise human varicella-zoster immunoglobulin (HVZIG) to be given intramuscularly as a single dose, which may prevent infection if given within 72 hours of exposure or attenuate an attack if given within 10 days of exposure. However, 90% of all adults in the UK show evidence of previous infection even without a previous history of infection.
 
Others at risk
Others at risk include HIV-positive patients and those who are immunosuppressed, either through illness or treatment. These may need to be given HVZIG or a DNA polymerase inhibitor (eg, aciclovir) or both (see the British National Formulary [BNF] for details).(5) This decision must be taken in conjunction with the patient's medical consultant or primary care provider. Neonates whose mothers have developed varicella between seven days before and one month after delivery will need to be referred appropriately for immunisation, and neonates who develop varicella are also at great risk.(2)

Herpes zoster or shingles
This is a viral inflammation caused by the reactivation of the (latent) chickenpox virus, which invades the dorsal root of the spinal nerves - when reactivated it causes blister-like lesions along the dermatomes (delineated areas of skin innervated by different spinal cord segments - each cord has a representative skin area). The virus migrates along the sensory fibres of the dorsal root causing pain and a rash in this area.(4) There is treatment available in the form of high-dose, frequent aciclovir or famciclovir; ideally to be effective this should be started at onset of the rash or at least within 36 hours (see BNF).
The elderly have an increased risk of morbidity with shingles due to the mild immunosuppression of old age and the increased likelihood of concurrent chronic disease - a problem in itself. It is vital that any ophthalmic and/or facial involvement be referred appropriately as an emergency as sensory use may be lost, resulting in blindness or facial paralysis. Postherpetic neuralgia may be reduced by the use of St John's wort, although its use has not yet been subjected to clinical trial and evidence is anecdotal only.(5,6)

Vaccines
There has to be a cost benefit to providing national immunisation, and at present this has been estimated as too expensive in the UK.(2) A vaccine is available on a "named-patient" basis for those at risk, such as children with leukaemia or those about to undergo a kidney transplant; however, this is as yet unlicensed so it cannot be administered under a Patient Group Direction. In the USA, the varicella vaccine has formed part of the national immunisation programme since 1996, when the disease routinely caused 50-100 deaths a year. Since that time the incidence has fallen dramatically, and it has been calculated that for every $1 the USA spends on the vaccine it saves $5.2 

References

  1. Ross A, Fleming D. Chicken pox increasingly affects pre-school children. Commun Dis Public Health 2000;3:213-5.
  2. Kassianos GC. Immunization - ­childhood and travel health. 4th ed. Oxford: Blackwell Science; 2001.
  3. Johnson G, Hill-Smith I, Ellis C.The minor illness manual. Oxford: Radcliffe Medical Press; 2000.
  4. Marieb E. Human anatomy and ­physiology. 3rd ed. California: Benjamin/Cummings; 1995.
  5. Lojeski E, Stevens R. Postherpetic neuralgia in the cancer patient. Curr Pain Headache Rep 2000;4:219-26.
  6. Ampofo K, Annunziato P. Varicella and zoster. Curr Treatment Options Inf Dis 2002;4:51-5.

Resources
Public Health Laboratory Service
W:www.phls.co.uk
British National Formulary (BNF)Provides UK healthcare ­professionals with authoritative and practical ­information on the selection and ­clinical use of medicines
W:www.bnf.org
The Shingles Support Society Part of the Herpes Viruses Association 41 North Road London N7 9DP
T:020 7607 9661
E:shinglespack@herpes.org.uk