Modeling of an influenza pandemic in Switzerland

• Unité de recherche: OFSP
• Numéro de projet: 05.000179
• Titre du projet anglais: Modeling of an influenza pandemic in Switzerland

Mots-clé (Anglais)

Influenza

Pandemic

Modeling

Description succincte (Allemand)

Erarbeitung eines mathematischen Models um verschiedene Szenarien einer Influenza Epidemie in der Schweiz zu evaluieren.

Description succincte (Anglais)

A stochastic model for predicting the number of influenza cases and deaths during a possible pandemic outbreak of this disease in Switzerland will be produced. The parameters of the model should be based on a transmission model developed using published data, especially from Mills et al. (2004) and Medema et al. (2004). The epidemiological model is to be developed using the Vensim® software and will render the number of influenza cases and the number of deaths per day for the whole duration of an epidemic (for a static population of ca 7 Mio inhabitants). Sensitivity analysis will be carried out to evaluate the influence of the parameter variation in model results. Results will thus be obtained by running ca. 200 Monte Carlo simulations, assuming random uniform distributions for different parameters.

Objectifs du projet (Allemand)

Erarbeitung eines mathematischen Models um verschiedene Szenarien einer Influenza Epidemie in der Schweiz zu evaluieren.

Objectifs du projet (Anglais)

In the context of the ‘Strategische Führungsübung 2005’ of Swiss federal office of public health, for newly emerging pandemics, the Section ‘Früherkennung und Epidemiologie’, ‘Fachstelle Methoden und Epidemiologie’, commissions the Swiss Tropical Institute to produce a mathematical model of the development of an Influenza epidemic in Switzerland. This model will render the number of cases and the number of deaths in Switzerland according to a most likely, as well as a best and worse case scenarios. The main objective is to know the dimensions and time evolution of such an event.

Résumé des résultats (Abstract) (Anglais)

The dynamic of an influenza pandemic in Switzerland was modelled using Vensim ® software. Values published from 1918 Influenza epidemic were used as input values for reproductive rate, attack rate, case fatality rate, incubation time and transmission period. In order to take into account uncertainties, the model incorporated these through using a most likely, a best and worst case scenario. The following results were obtained:

·      The size of the pandemic is not influenced the number of index cases. This parameter only affects the day of the peak of the epidemic. The study estimated that with 1 index case the peak is situated around the 50^th after the beginning of the outbreak. With 15 index cases the peak is situated around the 40^th day after the beginning.

·      With a case fatality rate of 1.5%, an incubation period of 1.9 days, a transmission period of 4.1 days, an attack rate of 20% and a reproductive number of 2.7, the most likely scenario of the model estimates that there are 1,472,835 new cases during the pandemic cycle

·      The most likely scenario estimates the number of deaths to be 22,093 persons.

Mise en oeuvre et application (Anglais)

This study constitutes a preliminary modeling exercise of an Influenza pandemic in Switzerland. It was carried out during the ‚Strategische Führungsübung 2005’ in only two days and as such, has some limitations.

Publications / Résultats (Anglais)

A short version of this study (or alternatively a modified extended version of it) could be published in the BAG bulletin.