écologie des virus influenza aviaires en Camargue - IRD

Influenza aviaires en Camarguemodel for eleven years and removed the first ten years from our analysis. Results are similarfor a transient length of one hundred and fifty years.We wanted to fit our model against disease data collected for all the transmissionpatterns tested in this study. First, we performed an exploratory fitting to define the mostplausible values. We found = 0.001 for inter­individual density­dependent transmission, = 250 for frequency­dependent transmission, = 5 for water­borne transmission and= and for continuum model. This exploratory fitting allowed us to select thecorrect range of values to be tested.We minimized the negative log­likelihood function between the prevalence ofinfectious individuals for each month from model outputs and prevalence of infectiousindividuals observed in our study area. Thus, we assumed that errors would be normallydistributed (e.g. Turchin and Hanski, 2001; Choisy et al. 2007) with a variance and weminimized:where f m is prevalence observed on the field, o m are prevalence from the model and xrepresents set of parameters. Indeed, we assumed that the field work had been performedduring the maximal disease activity each month. However, if we use the mean or the minimaldisease activity for each month from model outputs, we obtain also similar parameterestimations. We have selected random seed values: 0.0005