This paper puts forward a method for estimating the infection route and speed of influenza from the daily variations in the amount of influenza formulations supplied at distant city pharmacies. The cross-correlation function between the time variations at the pharmacies indicates as for the drug sales, how many days a pharmacy lags behind another pharmacy. The comparison of the time lags between the pharmacies can lead to the estimation of the infection route of influenza. Taking into account the distance between the locations of the pharmacies, we can calculate the infection speed of influenza. Three pharmacies located in Tokyo and its vicinity (Saitama and Kanagawa) are taken as an example. The thrust of this paper is to introduce the new strategy that can take full advantage of the information every pharmacy has in possession.