Varicella and herpes zoster in Madrid, based on the Sentinel General Practitioner Network: 1997-2004.
BACKGROUND
Varicella (chickenpox) is the primary disease caused by varicella-zoster virus. It is extremely contagious and is frequent in children. Indeed, in the absence of vaccination, a high proportion of the population is liable to contract it. Herpes zoster -more frequent among adults- is caused by reactivation of the latent virus. The objective of this study is to describe the status of and time trend for varicella and herpes zoster in the Madrid Autonomous Region prior to the introduction of the vaccine to the general population.


METHODS



METHODS
individualised varicella and herpes zoster case records kept by the Madrid Autonomous Region Sentinel General Practitioner Network for the period 1997-2004. Cumulative incidences, crude and standardised incidence rates, and age-specific rates of varicella and herpes zoster were calculated for each year. Kendall's Tau-b correlation coefficient was calculated to evaluate whether incidence displayed a time trend. Spectral density in the time series of weekly incidences was estimated using a periodogram.


RESULTS
Standardised annual varicella incidence rates ranged from 742.5 (95% CI: 687.2-797.7) to 1239.6 (95% CI: 1164.5-1313.4) cases per 100 000 person-years. Most cases affected children, though complications were more frequent in adults. Varicella incidence displayed an annual periodicity but no trend over time. Most herpes zoster cases occurred at advanced ages, with incidence registering a rising annual trend but no seasonality factor.


CONCLUSIONS
In the absence of vaccination, no significant changes in varicella incidence were in evidence recent years, though these were observed in the incidence of herpes zoster. Sentinel general practitioner networks are a valid instrument for surveillance of diseases such as varicella. Further varicella vaccination-coverage and vaccine-efficacy studies are called for.
Pérez-Farinós
Napoleón
N
Department of Epidemiology, Madrid Public Health Institute, Julián Camarillo 4B, Madrid, Spain. napoleon.perez@salud.madrid.org
Ordobás
María
M
García-Fernández
Cristina
C
García-Comas
Luis
L
Cañellas
Soledad
S
Rodero
Inmaculada
I
Gutiérrez-Rodríguez
Angeles
A
García-Gutiérrez
Juan
J
Ramírez
Rosa
R
D000293:Adolescent; D000328:Adult; D002644:Chickenpox / Q000150:complications / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D005194:Family Practice / Q000706:statistics & numerical data; D005260:Female; D006562:Herpes Zoster / Q000150:complications / Q000453:epidemiology*; D014645:Herpesvirus 3, Human / Q000472:pathogenicity*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012189:Retrospective Studies; D018571:Sentinel Surveillance; D013030:Spain / Q000453:epidemiology