[Analysis of an apparent cluster of Crohn's disease cases in Indre-et-Loire, France (1990-1999)].
BACKGROUND
Four cases of Crohn disease (CD) were diagnosed between 1990 and 1997 in children living in the same area in the Indre-et-Loire district (county A). The local population raised the hypothesis that an environmental source could be responsible for these cases. An investigation was carried out to assess the excess of cases and to identify their possible determinants.


METHODS
A case was defined as any new case of CD (European definition) that occurred between 1989 and 1998 in county A or in the adjacent county of the Vienne district. Case finding was done by contacting all hospital services, pediatricians and gastro-enterologists in the 2 districts. A Standardized Incidence Rate (SIR) was calculated for sex and age in adults and children using data from the Inflammatory Bowel Registry of northern France. Statistical significance was assessed by a test taking into account small samples. A descriptive study was carried out among pediatric cases.


RESULTS
Four pediatric cases and four adults were identified, all from county A. The SIR in adults was 0,45 (95% Confidence Interval [95% CI: 0.12-1.15). In children, the global SIR was 8,51 (95% CI: 2.29-21.79) and 19,05 (95% CI: 5.12-48.70) in county A. The descriptive study did not identify any exposure leading to a possible hypothesis concerning the origin of the cases.


CONCLUSIONS
This study has shown that the incidence of CD among children of the area was greater than observed in France and has permitted to establish a close relationship with the affected families, to implement a social approach to the problem and to limit rumors. It illustrates the interest of a systematic stepwise approach, which takes into consideration the anxiety of the local community. Cluster investigation should be integrated as part of the public health agencies activities. However, in most cases, despite an excess risk, results do not allow to conclude in terms of etiology.
Valenciano
M
M
Département Maladies infectieuses, Institut de Veille Sanitaire, 12, rue du Val-d'Osne, 94415 Saint-Maurice.
Gagnière
B
B
Maurage
C
C
de Valk
H
H
Desenclos
J-C
JC
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D015331:Cohort Studies; D003424:Crohn Disease / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged