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[Shigellosis in Amsterdam, 1991-1998: incidence and results of contact tracing]
M P Vermaak1, M W Langendam, J A van den Hoek
1Gemeentelijke Geneeskundige en Gezondheidsdienst, divisie Volksgezondheid en Milieu, Amsterdam.
Objective:
To determine the incidence of reported shigellosis in Amsterdam (1991-1998) and the factors related to the secondary attack rate of shigellosis.
Design:
Retrospective.
Methods:
From an automated data bank data were collected on all registered shigellosis patients in Amsterdam in the period 1991-1998, and their contacts found by contact tracing.
Results:
567 Patients with shigellosis had been reported and a Shigella infection has been diagnosed in 96 of the 983 contacts. The annual incidence decreased statistically significantly from 13 to 8/100.000. 329 males and 334 females were infected. The highest number of cases was found in children from 0-4 years and among adults from 20-34 years. Of the 663 patients 106 (16%) required hospitalization; for children under 7 this proportion was 30% (32/108). Among the contacts (excluding the 14 contacts with the same foreign source and the same first sickness day as the index patient) the secondary attack rate was 8%. Young age, of both the patient and the contact was independently related to a higher secondary attack rate.
Conclusion:
With contact tracing for shigellosis a large number of secondary infections were found. Given the high infection rate and large number of hospitalisations among children, contact tracing should focus at this young age group.