`titrebSurveiller et s’unir ?`/titrebAfter World War II, the World Health Organization Influenza Programme conducted the first international coordination in the fight against influenza. Faced with the variability of the virus, WHO developed a network of laboratories to monitor the human strains in circulation. Two decades later, the elucidation of the origin of human pandemics with a bundle of evidence implicating the role of reservoir animals greatly expanded the scope of surveillance. This article describes how the influenza surveillance developed an ecological approach to the disease through the recruitment of new actors, helped by a standardization of working methods in the network. Facing the biodiversity of species infected with the virus, research on disease ecology has contributed to a new focus on unstable ecological balance shown by the circulation of viruses between species, breaking with the optimism of control of infectious diseases, which began in the late 19th century.