Explanation Of Condition

Chickenpox, also known as varicella, is a common childhood illness caused by infection with Varicella zoster virus. This is a DNA virus from the herpes family. The mode of transmission is mainly via respiratory droplets or by direct contact and is therefore highly contagious. Reactivation of the virus, which has remained latent in the dorsal root or cranial nerve ganglion, causes shingles. This often occurs many years after the initial infection. Chickenpox may be acquired by contact with shingles but this is less common.

Clinical features of chickenpox include a mild febrile illness, associated with malaise and the development of a characteristic vesicular rash. The rash is pruritic, the vesicles appear in waves and typically vesicles, pustules and crusted lesions appear together. The illness usually lasts 7-10 days. There is increased morbidity and mortality in pregnancy compared with non-pregnant, especially as the pregnancy advances2.

Shingles is characterised by an eruption of painful vesicles covering an area of skin corresponding to one or two sensory nerves, particularly the thoracic nerves, but may affect the cranial nerves, e.g. ophthalmic. If the dorsal root ganglion is affected then the rash may extend from the middle of the back to the chest wall.

The incubation period is 10-12 days, however the infective period extends from 48 hours prior to the appearance of the rash until all the vesicles have crusted over.

Immunity is solid and long-lasting and as the infection is so commonly acquired in childhood over 90% of the antenatal population is immune to the virus3. Of those with uncertainty regarding their immune status, 80% will have IgG antibodies on serum testing and will therefore be immune4.

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