Journal of Infectious Diseases
Volume 205 Issue 9 May 1, 2012
http://www.journals.uchicago.edu/toc/jid/current

EDITORIAL COMMENTARIES
Karen C. Bloch and James G. Johnson
Editor’s Choice: Varicella Zoster Virus Transmission in the Vaccine Era: Unmasking the Role of Herpes Zoster
J Infect Dis. (2012) 205(9): 1331-1333 doi:10.1093/infdis/jis214

Extract
Varicella (chickenpox) is a highly contagious disease caused by varicella zoster virus (VZV). After infection, the virus remains dormant in sensory dorsal root ganglia. Reactivation of latent VZV is associated with cutaneous disease occurring in ≥1 dermatomes, termed herpes zoster (HZ). Historically, HZ has been considered significantly less infectious than varicella and has not been thought to play an important role in person-to-person transmission. Since the licensure of the varicella vaccine in 1995 and the more recent recommendation that a second dose of vaccine be given to children aged 4–6 years [1], the epidemiology of pediatric varicella infection has shifted dramatically [2].

Efforts to quantify the burden of varicella in the community since vaccine licensure have been hindered by the absence of mandatory case-based reporting in most jurisdictions [3]. The article by Viner et al in this issue of the journal [4] provides important new insights into the epidemiology and transmissibility of VZV in a highly immunized, healthy pediatric population. The authors analyzed data obtained through a combination of active and passive surveillance for both varicella and HZ in Philadelphia schools and day care centers during 7 academic years. Cases were linked to the Philadelphia Department of Public Health immunization registry for ascertainment of vaccine status. Through this comprehensive surveillance system, 2296 cases of VZV-associated infection were identified, with 28% categorized as secondary varicella.

Much of what is known about VZV transmission dynamics in the community comes from outbreak investigations at elementary schools or day care centers. In these settings, varicella attack rates among children who had previously received a single dose of varicella vaccine ranged from 12%–42% [5–7]. A recent report found that …

VIRUSES
Kendra Viner, Dana Perella, Adriana Lopez, Stephanie Bialek, Claire Newbern, Rodrerica Pierre, Niya Spells, and Barbara Watson
Editor’s Choice: Transmission of Varicella Zoster Virus From Individuals With Herpes Zoster or Varicella in School and Day Care Settings
J Infect Dis. (2012) 205(9): 1336-1341 doi:10.1093/infdis/jis207

Abstract
(See the editorial commentary by Bloch and Johnson, on pages 1331–3.)

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.