Experimental surveillance using data on sales of over-the-counter medications--Japan, November 2003-April 2004.
OBJECTIVE
This report describes a study to explore the possibility of using data on sales of over-the- counter (OTC) medications as part of a routine syndromic surveillance system aimed at early detection of infections of public health concern. A retrospective evaluation was conducted of sales of OTC medications used to treat the common cold. This report discusses the correlation of these data to influenza activity in Japan during the 2003-04 influenza season and evaluates the potential of using such data to predict influenza epidemics.


METHODS
Data from approximately 1,100 pharmacies throughout Japan collected during November 2003-April 2004 were analyzed. OTC sales data were compared with influenza incidence data (one weekly and two daily data sets) to determine correlations and predictability. Adjusted R-square was used as an index of goodness of-fit in the estimation. Data reflecting daily influenza activity were obtained from the National Surveillance of Daily Influenza Outpatients and the Mailing List-Based Influenza Epidemic Database. National sentinel surveillance data for influenza from approximately 5,000 sites nationwide also were analyzed.


RESULTS
Although a correlation was demonstrated between sales of OTC medications used to treat the common cold and concurrent influenza activity, analysis of sales data alone was not sufficient to determine influenza activity in advance even when sales promotion effects were excluded from the analysis.


CONCLUSIONS
Because visiting a health-care provider costs more than purchasing OTC medications, the hypothesis was formed that an ill person will purchase OTC medications first and visit a physician only if the condition does not resolve or worsens. The results of this study do not provide any clear evidence to support this hypothesis. For this reason, OTC sales do not appear to be a good candidate for a national real-time detection system for influenza epidemics in Japan.
Ohkusa
Yasushi
Y
Infectious Disease Surveillance Center, National Institute of Infectious Diseases, Tokyo, Japan. ohkusa@nih.go.jp
Shigematsu
M
M
Taniguchi
K
K
Okabe
N
N
D003132:Commerce / Q000706:statistics & numerical data*; D004196:Disease Outbreaks / Q000517:prevention & control*; D004363:Drug Utilization; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology; D007564:Japan / Q000453:epidemiology; D004366:Nonprescription Drugs; D010594:Pharmacies / Q000706:statistics & numerical data; D011159:Population Surveillance / Q000379:methods*; D040442:Public Health Informatics; D012189:Retrospective Studies
D004366:Nonprescription Drugs