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40 - VZV: persistence in the population: transmission and epidemiology
- from Part III - Pathogenesis, clinical disease, host response, and epidemiology: VZU
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- By Jane Seward, National Immunization Program Centers for Disease Control and Prevention, Atlanta, GA, USA, Aisha Jumaan, National Immunization Program Centers for Disease Control and Prevention, Atlanta, GA, USA
- Edited by Ann Arvin, Stanford University, California, Gabriella Campadelli-Fiume, Università degli Studi, Bologna, Italy, Edward Mocarski, Emory University, Atlanta, Patrick S. Moore, University of Pittsburgh, Bernard Roizman, University of Chicago, Richard Whitley, University of Alabama, Birmingham, Koichi Yamanishi, University of Osaka, Japan
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- Book:
- Human Herpesviruses
- Published online:
- 24 December 2009
- Print publication:
- 16 August 2007, pp 713-734
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- Chapter
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Summary
Like other herpes viruses, varicella zoster virus (VZV) causes disease due to the primary infection (varicella) and due to reactivation (herpes zoster). However, VZV differs from other herpes viruses in causing primary and reactivation infections that are easily recognized clinical diseases, even by the lay public. Because of this, the epidemiology of varicella and herpes zoster has been well described from clinically recognized disease (incidence, severe disease outcomes and deaths) with seroprevalence data providing additional information on the epidemiology of varicella especially in populations where varicella disease history may not be available.
Varicella occurs worldwide with ongoing endemic transmission in areas where populations are sufficiently large to support such transmission. However the epidemiology of varicella varies between temperate and tropical climates (Lee, 1998). Universal childhood vaccination programs have changed the epidemiology of varicella in countries implementing such programs with significant declines in disease. Most experience has been gained in the United States where a varicella vaccination program was initiated in 1995. Herpes zoster infections also occur throughout the world although the epidemiology of herpes zoster is less well described globally. Because the incidence of herpes zoster increases dramatically with age, countries with lower life expectancies may have lower health burdens due to this disease. A vaccine for prevention of herpes zoster and post-herpetic neuralgia was licensed in the USA in May, 2006 (Oxman et al., 2005). This chapter reviews pre- and post-vaccine epidemiology of varicella and herpes zoster.
10 - Epidemiology of varicella
- from Part III - Epidemiology and Clinical Manifestations
- Edited by Ann M. Arvin, Stanford University School of Medicine, California, Anne A. Gershon, Columbia University, New York
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- Book:
- Varicella-Zoster Virus
- Published online:
- 02 March 2010
- Print publication:
- 23 November 2000, pp 187-205
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Summary
Although varicella occurs worldwide, the epidemiology of the disease differs in temperate compared with tropical climates. Moreover, as vaccine use increases in countries such as the United States, in which the vaccine is recommended as part of the routine childhood immunization schedule (Committee of Infectious Diseases, 1995; CDC, 1996), the epidemiology of the disease will change. This chapter summarizes methodological issues that must be considered when comparing results of varicella studies; reviews varicella epidemiology in the pre-vaccine era for temperate and tropical regions; and outlines the likely changes in the epidemiology of disease following widespread use of vaccine.
Methodological issues
Reports of varicella incidence differ in the methods used to determine the number of cases; the method used impacts completeness of ascertainment and, therefore, estimates of age-specific incidence and age distribution of cases. Because varicella is easily diagnosed by the lay public, information on disease incidence can be collected from household-based surveys (Guess et al., 1986; Finger et al., 1994; Yawn et al., 1997). Data collected from such surveys with a defined recall period, optimally one year or less, are more complete than data obtained from medical record review or passive reporting (surveillance) systems. In surveillance systems, completeness of ascertainment may vary by age, reflecting age- related differences, such as the proportion of patients seeking health care. Variations in completeness of reporting by age have been documented by comparing varicella cases reported via a reportable communicable disease system with cases detected by a household survey over the same time period (Sydenstricker & Hedrick, 1929). Reporting was more complete for adults (50%) than for school-aged children (25%) and was lowest for preschool children (12%).