title: Spreading patterns of the influenza A (H1N1) pandemic.
abstract: We investigate the dynamics of the 2009 influenza A (H1N1/S-OIV) pandemic by analyzing data obtained from World Health Organization containing the total number of laboratory-confirmed cases of infections--by country--in a period of 69 days, from 26 April to 3 July, 2009. Specifically, we find evidence of exponential growth in the total number of confirmed cases and linear growth in the number of countries with confirmed cases. We also find that, i) at early stages, the cumulative distribution of cases among countries exhibits linear behavior on log-log scale, being well approximated by a power law decay; ii) for larger times, the cumulative distribution presents a systematic curvature on log-log scale, indicating a gradual change to lognormal behavior. Finally, we compare these empirical findings with the predictions of a simple stochastic model. Our results could help to select more realistic models of the dynamics of influenza-type pandemics.
authors.affiliation: Departamento de Física, Universidade Estadual de Maringá, Maringá, Paraná, Brazil. junior@dfi.uem.br
authors.forename: Sergio
authors.initials: S
authors.lastname: de Picoli Junior
authors.forename: Jorge Juarez Vieira
authors.initials: JJ
authors.lastname: Teixeira
authors.forename: Haroldo Valentin
authors.initials: HV
authors.lastname: Ribeiro
authors.forename: Luis Carlos
authors.initials: LC
authors.lastname: Malacarne
authors.forename: Ricardo Paupitz Barbosa
authors.initials: RP
authors.lastname: dos Santos
authors.forename: Renio
authors.initials: R
authors.lastname: dos Santos Mendes
mesh_terms: D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D058873:Pandemics / Q000706:statistics & numerical data