This article describes the findings recorded by an early warning system, the Regional Influenza Surveillance Groups (GROG), during the 1995–1996 winter season, which was marked by the simultaneous circulation of influenza A (H1N1), A (H3N2), B, and RSV (respiratory syncytial virus). By comparing clinical and virological data, the GROG was able to distinguish between the effects of influenza and those of RSV, predict the influenza epidemic two months before the peak of the outbreak, and encourage physicians to accelerate the pace of vaccinations for at-risk patients. (adapted from the text).