Varicella: Vaccine Preventable Diseases Surveillance Standards

Overview

Varicella-zoster virus (VZV) causes both varicella (chickenpox) by primary infection and herpes zoster (HZ or shingles) by endogenous reactivation from latency. VZV circulates worldwide. Acquisition of infection tends to be at a younger age in temperate countries (> 90% infected by adolescence in absence of vaccination programme), compared to an older distribution in tropical countries. Varicella shows a winter/spring or cool/dry month predominance, and can occur in large outbreaks every 2–5 years. VZV is highly contagious with secondary attack rates from varicella cases ranging from 61–100%. The virus spreads person-to-person primarily by inhalation of aerosols from vesicular fluid of skin lesions, by direct contact with rash and possibly by infected respiratory tract secretions. Without vaccination, almost everyone in the population acquires wild-type varicella infection by adulthood.