Abstract
The aim of this paper is to compare the geographical routes and speeds of influenza propagation in and around Tokyo, including Kanagawa, Saitama, Tochigi and Fukushima prefectures, in the seasons of 2003/2004, 2004/2005 and 2005/2006. Each season ranges from November 1st to October 31st. The propagation pattern is estimated from the daily variations in the sales amount of anti-influenza drug at about 30 pharmacies in the area. The time lags (day) of influenza infection periods between distant pharmacies are calculated by the cross-correlation functions of the drug sales at the pharmacies. We conclude that the influenza infection spread from the urban area of Tokyo to its suburbs (Saitama and Kanagawa) along the railway systems in all the seasons examined. However, no definite infection routes can be found in Tochigi and Fukushima. The infection periods of adults are contrasted with those of children in individual observation sites.
