title: Transmission of varicella zoster virus from individuals with herpes zoster or varicella in school and day care settings.
abstract: BACKGROUND
  Because the varicella incidence has declined following varicella vaccine licensure, herpes zoster (HZ) cases may play a larger role in varicella zoster virus (VZV) transmission. We investigated how HZ and varicella cases contribute to the varicella incidence in schools and day care centers.
  
  
  METHODS
  Surveillance data collected in Philadelphia during September 2003-June 2010 were analyzed. A varicella case was considered to be sporadic if it was reported from a school or day care facility >6 weeks after or ≥10 days before other reports of VZV transmission. A varicella case was considered to be secondary if it occurred 10-21 days after report of a case of HZ or sporadic varicella. Analysis compared VZV transmission from individuals with HZ or sporadic varicella, stratified by varicella vaccination status and disease severity.
  
  
  RESULTS
  Of 290 HZ cases reported, 27 (9%) resulted in 84 secondary varicella cases. Of 1358 sporadic varicella cases reported, 205 (15%) resulted in 564 secondary varicella cases. Approximately half of the HZ and sporadic varicella cases resulted in single secondary cases. The proportion of individuals who had secondary cases with mild disease was similar for those exposed to HZ and those exposed to varicella (70% and 72%, respectively). VZV transmission was highest from unvaccinated individuals with sporadic varicella (P < .01).
  
  
  CONCLUSIONS
  VZV transmission from individuals with HZ contributes to varicella morbidity. More research is needed to understand risk factors and guide recommendations for preventing VZV transmission from individuals with HZ.
authors.affiliation: Division of Disease Control, Philadelphia Department of Public Health, Pennsylvania 19146, USA. kendra.viner@phila.gov
authors.forename: Kendra
authors.initials: K
authors.lastname: Viner
authors.forename: Dana
authors.initials: D
authors.lastname: Perella
authors.forename: Adriana
authors.initials: A
authors.lastname: Lopez
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bialek
authors.forename: Claire
authors.initials: C
authors.lastname: Newbern
authors.forename: Rodrerica
authors.initials: R
authors.lastname: Pierre
authors.forename: Niya
authors.initials: N
authors.lastname: Spells
authors.forename: Barbara
authors.initials: B
authors.lastname: Watson
mesh_terms: D002644:Chickenpox / Q000453:epidemiology* / Q000276:immunology / Q000517:prevention & control / Q000635:transmission*; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D006562:Herpes Zoster / Q000453:epidemiology* / Q000276:immunology / Q000517:prevention & control / Q000635:transmission*; D014645:Herpesvirus 3, Human / Q000302:isolation & purification* / Q000472:pathogenicity*; D006801:Humans; D015994:Incidence; D015143:Philadelphia / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D012574:Schools; D014611:Vaccination / Q000379:methods