The herpes virus varicella-zoster is spread by the respiratory route; its incubation period is about 14 days.
Slight malaise is followed by the development of papules, which turn rapidly into clear vesicles, the contents of which soon become pustular. Over the next few days the lesions crust and then clear, some-times leaving white depressed scars. Lesions appear in crops, are often itchy, and are most profuse on the trunk and least profuse on the periphery of the limbs (centripetal). Second attacks are rare. Vari-cella can be fatal in those who are immunologically compromised.
• Pneumonitis, with pulmonary opacities on X-ray.
• Secondary infection of skin lesions.
• Haemorrhagic or lethal chickenpox in the immunocompromised.
Smallpox, mainly centrifugal anyway, has been univer-sally eradicated, and the diagnosis of chickenpox is seldom in doubt.
None are usually needed.
Aciclovir, famciclovir and valaciclovir should be reserved for severe attacks and for immunocompromised patients; for the latter, pro-phylactic aciclovir can also be used to prevent disease if given within a day or two of exposure. In mild attacks, calamine lotion topically is all that is required. A live attenuated vaccine is now available, and being more widely used. It is not universally effective and should not be given to patients with immunodeficien-cies or blood dyscrasias who might not be able to resist even the attenuated organism.