[Influenza A (H1N1) 2009 and uncertainties: lessons from a pandemic].

During a pandemic, public health specialists base their recommendations on previous data and more or less complex epidemiological models. By contrast, a virus replicates according to its own rules and biological properties that do not consider epidemiological models. Recent experience with influenza virus A (HINI) 2009 well demonstrates that public health models have a limited ability to predict the type and the pattern of a future pandemic. It is rather the virus that dictates the rules.