Clinical features

Features include: (1,2)

• 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
  • this period may be prolonged in immunocompromised patients
  • 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
• 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 fulminating varicella pneumonia
• neonates and immunosuppressed individuals – there is an increased risk of developing disseminated or haemorrhagic varicella
• 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

Reference:

1. UK Health Security Agency. The Green Book: Varicella. Jun 2019 [internet publication].
2. Freer G, Pistello M. Varicella-zoster virus infection: natural history, clinical manifestations, immunity and current and future vaccination strategies. New Microbiol. 2018 Apr;41(2):95-105.