A Method for Estimating Infection Route and Speed of Influenza

Abstract

This paper puts forward a method for estimating the infection route and speed of in‰uenza from the daily variations in the amount of in‰uenza 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 in‰uenza. Taking into account the distance between the locations of the pharmacies, we can calculate the infection speed of in‰uenza. 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.

Factor Analysis of Drug Supply Time Series at Pharmacies

“…[4][5][6][7][8][9][10] Quite recently, a new method was proposed for estimating the geographical route and speed of influenza propagation from prescription drug sales at distant pharmacies. 11) The infection pattern in three seasons in and around Tokyo was investigated. 12) An analytical challenge in the above studies is to identify a signal indicating an outbreak of disease amid the ubiquitous background noise in the data.…”

Geographical Pattern of Influenza Propagation in Tokyo and Its Neighborhood in Three Seasons

“…[1][2][3][4][5][6][7] Recently, a new method for estimating the route and speed of influenza propagation was put forward. [13][14][15] The most prominent features of this method are the mathematical technique and sources of disease information. The fundamental assumption is that the health conditions of people are reflected by the drug sales at pharmacies.…”

“…The fundamental assumption is that the health conditions of people are reflected by the drug sales at pharmacies. 13,14) In the previous paper, 15) the time series of drug sales were collected from fourteen community pharmacies and analyzed with the cross-correlation function. The study led to the conclusion that the influenza infection appears to have spread from the urban area of Tokyo to its suburbs at an averaged speed of 3.5 km/day in the period from November 1st, 2004 to October 31st, 2005 (04/05 season).…”

Smoothing of Correlation Functions in the Estimation of the Order of Influenza Infection between Adults and Children

“…[1][2][3][4][5][6] The techniques of spectral analysis has also been used for common purposes, e.g., power spectrum, auto-correlation function and cross-correlation function. [7][8][9][10][11][12][13][14] The cross-correlation functions are concerned with the time lag of similar or correlated phenomena which occur in distant places or under different situations.…”

“…Unfortunately, however, the determination of the time lags can be obscured by the hebdomadal frequencies which originate from the life style of people in recent human society. 13,14) For example, the prescription of the influenza anti-viral agent for children was observed to concentrate on Sundays and Mondays at a pharmacy, even if it is open throughout the year.…”