Bacaër Nicolas auteur aut IRD Dads E. A. auteur aut IRD text journalArticle eng text/pdf born digital access The basic reproduction number R (0) has been used in population biology, especially in epidemiology, for several decades. But a suitable definition in the case of models with periodic coefficients was given only in recent years. The definition involves the spectral radius of an integral operator. As in the study of structured epidemic models in a constant environment, there is a need to emphasize the biological meaning of this spectral radius. In this paper we show that R (0) for periodic models is still an asymptotic per generation growth rate. We also emphasize the difference between this theoretical R (0) for periodic models and the "reproduction number" obtained by fitting an exponential to the beginning of an epidemic curve. This difference has been overlooked in recent studies of the H1N1 influenza pandemic. specialized Basic reproduction number Seasonality Epidemics H1N1 influenza 052 020 62 5 741-762 2011 0303-6812 https://www.documentation.ird.fr/hor/fdi:010053487 10.1007/s00285-010-0354-8 0303-6812 [F B010053487] https://www.documentation.ird.fr/hor/fdi:010053487 https://www.documentation.ird.fr/intranet/publi/2011/05/010053487.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2011-05-31 2017-08-23 fdi:010053487 fre