Varicella zoster (chickenpox)

Varicella is an acute, highly infectious disease caused by the varicella zoster virus (VZV) which also causes shingles. It is typically a disease of childhood (Macartney and McIntyre, 2008) with an incubation period of 7–21 days.

It is communicable from 5 days before a rash develops until 6 days after. The disease is characterised by a widespread maculopapular rash which often starts on the trunk and then moves to the limbs. Lesions are often seen at all stages at once: vesicles, papules and crusted lesions. Fever and general malaise are also present.

Management

1. Treatment is supportive.
2. Paracetamol may be given for pyrexia.
3. Traditionally lotions, for example calamine lotion, are used. The effect of calamine lotion on pruritis has not been evaluated but it has a good safety profile and Tebruegge et al. (2006) report some symptomatic relief. They found limited evidence to support the use of systemic antihistamines in this context.
4. Lukewarm baths may provide some relief and light cotton clothing is probably more comfortable (Shuru, 2003).
5. Scabs should not be picked but allowed to fall off spontaneously.
6. Children with sores in their mouths may be reluctant to eat or drink, so small amounts of clear liquids should be encouraged frequently.
7. Aciclovir can reduce the number of days with fever in otherwise healthy children but its effect on soreness and itching is not certain (Klassen et al., 2005).
8. Live attenuated varicella vaccines are now licensed for use in some countries (not the UK) and are a potential strategy for the prevention of morbidity from varicella infection. Macartney and McIntyre’s 2008 review of the efficacy and safety of vaccines for the post-exposure prophylaxis against varicella shows that varicella vaccine administered within 3 days to children following household contact with a varicella case reduced infection rates and severity of cases but did not adequately address safety aspects.
9. Neonates with chickenpox should be treated with parenteral aciclovir regardless of immune function to reduce the risk of severe disease.
10. Neonates and children and adults who are immunocompromised and have been exposed to the virus may require prophylaxis with varicella-zoster immunoglobulin (VZIG).
    
    

Complications
In healthy children, the disease is mostly selflimiting. The most common complication is secondary bacterial infection (Macartney and McIntyre, 2008). However, there are the more serious well-recognised complications of pneumonia and encephalitis, dehydration, hepatitis and ataxia and these usually lead to hospitalisation. Women who contract varicella in the first 20 weeks of pregnancy have a 2% risk of the foetus developing congenital varicella syndrome with women who contract varicella in the last trimester being at increased risk of pneumonia. The onset of varicella in pregnant women from 5 days prior to delivery to 2 days after can result in neonatal varicella in 17–30% (Macartney and McIntyre, 2008).

VZV also remains dormant in the dorsal ganglia of individuals and can reactivate to cause herpes zoster. Primary infection usually provides lifetime immunity but secondary infections do occur.

Immunocompromised patients are at particular risk from primary VZV infection or reactivation.