Résumés
Résumé
Les modélisations de l’épidémie du variant de la la maladie de Creutzfeldt-Jakob (vMCJ) dû à l’agent de l’encéphalopathie spongiforme bovine (ESB) font toutes appel à un « rétro-calcul » qui relie par une équation mathématique simple: (1) le nombre de personnes infectées; (2) la distribution des dates d’infection; et (3) la distribution de la durée d’incubation. Les modèles se distinguent par les hypothèses et les techniques utilisées pour définir ces trois paramètres inconnus. En ce qui concerne la durée d’incubation, certains modèles font appel à des scénarios fixant arbitrairement sa valeur moyenne et sa variabilité; d’autres, plus récents, cherchent à les estimer en s’appuyant sur l’incidence du vMCJ entre 1995 et 2001. Malgré de nombreuses différences méthodologiques, les résultats des modélisations sont très cohérents. Pour des durées d’incubation de 15 à 20 ans, valeur obtenue par tous les modèles ayant cherché à estimer ce paramètre à partir de l’incidence du vMCJ, les cinq modèles prédisent une épidémie de 500 à 2000 cas au Royaume-Uni.
Summary
The back-calculation technique is used in all studies aimed at predicting the future incidence of the variant Creutzfeldt-Jakob disease (vCJD) caused by the agent of bovine spongiform encephalopathy (BSE). The back-calculation method uses a simple mathematical equation which relates (1) the number of infected persons ; (2) the distribution of infection times ; and (3) the incubation period distribution. The different studies considered in this review differ essentially in their assumptions and in the techniques used to assign values to the unknown parameters. For the incubation period distribution, some studies use scenario based-technique analysis where the mean and the variance are arbitrarily fixed. In other recent studies, these parameters are estimated using the observed incidence of vCJD between 1995 and 2001. Despite several methodological differences, the results obtained from these different studies are consistent. Albeit the methodology used, for mean incubation periods between 15 and 20 years - the best estimates found in the « estimation » studies - the five models considered in this review predict an epidemic size between 500 and 2000 cases in the United Kingdom.
Parties annexes
Références
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