Abstract
Background
In Ontario, infectious gastrointestinal illness (IGI) reporting can be represented by a linear model of several sequential steps required for a case to be captured in the provincial reportable disease surveillance system. Since reportable enteric data are known to represent only a small fraction of the total IGI in the community, the objective of this study was to estimate the under-reporting rate for IGI in Ontario.
Methods
A distribution of plausible values for the under-reporting rate was estimated by specifying input distributions for the proportions reported at each step in the reporting chain, and multiplying these distributions together using simulation methods. Input distributions (type of distribution and parameters) for the proportion of cases reported at each step of the reporting chain were determined using data from the Public Health Agency of Canada’s National Studies on Acute Gastrointestinal Illness (NSAGI) initiative.
Results
For each case of enteric illness reported to the province of Ontario, the estimated number of cases of IGI in the community ranged from 105 to 1,389, with a median of 285, and a mean and standard deviation of 313 and 128, respectively.
Conclusions
Each case of enteric illness reported to the province of Ontario represents an estimated several hundred cases of IGI in the community. Thus, reportable disease data should be used with caution when estimating the burden of such illness. Program planners and public health personnel may want to consider this fact when developing population-based interventions.
MeSH terms: Gastroenteritis, infectious disease reporting, surveillance, Ontario, Canada
Résmé
Contexte
En Ontario, la notification des maladies gastrointestinales infectieuses (MGI) peut être représentée par un modèle linéaire illustrant la marche à suivre pour saisir chaque cas dans le système provincial de surveillance des maladies à déclaration obligatoire. Comme on sait que les données sur les entéropathogènes à déclaration obligatoire ne représentent qu’une petite fraction de toutes les MGI présentes dans la collectivité, notre étude visait à estimer le taux de sous-notification des MGI en Ontario.
Méthode
Nous avons estimé la répartition des valeurs plausibles du taux de sous-notification en spécifiant les répartitions des paramètres d’entrée selon les proportions déclarées à chaque étape de la chaîne de notification, puis en multipliant ces répartitions entre elles à l’aide de méthodes de simulation. Grâce aux données de l’Étude nationale des maladies gastro-intestinales aiguës (ENMGA) de l’Agence de santé publique du Canada, nous avons déterminé les répartitions d’entrée (genre de répartition et paramètres) pour la proportion de cas déclarés à chaque étape de la chaîne de notification.
Résultats
Pour chaque cas de maladie entérique déclaré en Ontario, le nombre estimatif de cas de MGI dans la collectivité se situe entre 105 et 1 389, la médiane étant de 285, avec une moyenne de 313 et un écart-type de 128.
Conclusions
Selon nos estimations, chaque cas de maladie entérique déclaré en Ontario correspond à plusieurs centaines de cas de MGI présents dans la collectivité. Les données sur les maladies à déclaration obligatoire doivent donc être utilisées avec prudence lorsqu’on estime le fardeau de ces maladies. Les planificateurs de programmes et les intervenants en santé publique devraient en tenir compte lorsqu’ils élaborent des interventions pour l’ensemble de la population.
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