Primary infection caused by varicella-zoster virus (VZV) is manifest by varicella (chickenpox), while reactivation of latent virus causes herpes zoster (shingles). In immunocompetent children, varicella is usually not a serious disease, but can cause severe morbidity and mortality in adults and in immunocompromised individuals. Similarly, herpes zoster is associated with much greater morbidity in patients with impaired cell-mediated immune responses. In addition, herpes zoster can cause prolonged pain (postherpetic neuralgia) that can be very difficult to manage, particularly in older individuals. The outcomes of varicella and herpes zoster, especially in immunocompromised patients, have been dramatically improved by the development of safe and effective antiviral drugs with potent activity against VZV. Early drugs with modest efficacy and substantial toxicity (e.g., interferon, vidarabine, etc.) have been replaced by antiviral agents with enhanced in vitro activity, improved pharmacokinetic properties, and excellent safety profiles.
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