Clinical features

Features include:

• the incubation period is from 14 up to 21 days
  • chicken pox is infectious from a few days before the onset of rash develops and not more than six days after first lesions appear (1)
  • this period may be prolonged in immunocompromised patients (2)
  • chickenpox is very infectious - cases on a ward ought to be isolated to prevent cross infection
• the rash begins as macular lesions which develop into papular, or vesicular lesions (filled with fluid) and later becomes pustular
• chickenpox rash has a centripetal distribution - mostly on the face and trunk and sparsely on the limbs
• there is erythema around the lesions and they are intensely itchy
• usually the rash peaks at around 48 hours in immunocompetent people
• vesicles dry and crust over, and sometimes scar if scratched to excess
• oropharynx and genital tract mucous membranes may be involved as well
• new lesions can emerge for up to 5 days (3)
• a haemorrhagic rash may occur in immuno-suppressed patients

In children under 10 years, the disease is usually mild and self limiting, but a more severe infection can be seen in

• adults - especially in pregnant women and in smokers since they are at an increased risk of developing fulminanting varicella pneumonia
• neonates and immunosupressed individuals – there is an increased risk of developing disseminated or haemorrhagic varicella (2)

Signs of severe infections include:

• respiratory symptoms (clinical respiratory signs are often absent).
• densely cropping vesicles
• haemorrhagic rash
• bleeding from gums, haemoptysis, GI bleeding
• any neurological changes - cerebellar signs, encephalopathy
• persisting fever with new vesicles >6 days after onset (2)

Reference:

• (1) Institute for Child Health, Great Ormond Street Hospital for Children NHS Trust.
• (2) Department of Health 2006. The green book - Varicella
• (3) Tunbridge AJ et al. Chickenpox in adults - Clinical management. Journal of Infection 2008;57:95e102