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Varicella zoster virus: natural history and current therapies of varicella and herpes zoster.

The natural history of varicella zoster virus (VZV) infection and the molecular mechanisms of viral pathogenesis are incompletely understood. Although no animal model yet reproduces all aspects of VZV infection, recently developed models of VZV infection, and the creation of genetically altered VZV recombinants, are yielding new information about primary viraemia and latency. During viraemia, T-cells transport VZV to the skin, where cell-free viral replication facilitates person-to-person spread and transmission to the neurons where latency is established. The alternate viral pathways of lytic infection or latency appear to be cell-type determined and involve both host and viral components. Antiviral therapy for varicella is safe and efficacious, and as varicella in children is usually mild, treatment is generally recommended only for adolescents and adults with varicella. Treatment is recommended for all individuals with herpes zoster, especially those aged over 50 years. For some varicella and zoster cases, aciclovir, the original standard, is being replaced by valaciclovir and famciclovir as preferred therapies. For herpes zoster, bromovinyl deoxyuridine (brivudin) has been added to the list of treatment options for immunocompetent individuals, but is contraindicated in patients with cancer. Antiviral therapy will still have a role in the treatment of disease caused by VZV even after the widespread implementation of vaccination programmes for both chickenpox and herpes zoster.