Introduction

It is quite unusual for a single virus to be responsible for three distinct clinical entities, not to mention many unrecognized forms of disease. The varicella-zoster virus (VZV) is such a virus. It causes varicella or chickenpox, usually in childhood; is sometimes responsible for zoster or shingles, usually in late adulthood; and, in some cases, sets the scene for postherpetic neuralgia (PHN) or postzosterian pain (Weller; names in parentheses denote authors of papers in this supplement). All these disorders are relatively poorly understood. The virus itself is very difficult to study and grows poorly in tissue culture. It is extremely difficult to construct experimental mutants that would assign precise pathogenic roles to its individual genes. VZV is generally considered to be similar to other Herpesviridae, mostly to the best known of them all: herpes simplex virus (HSV). However, besides the fact that VZV and HSV are responsible for different diseases, it is becoming increasingly clear …