Persons using assistive technology might not be able to fully access information in this file. For assistance, please send e-mail to: firstname.lastname@example.org. Type 508 Accommodation and the title of the report in the subject line of e-mail.
Monitoring Over-the-Counter Pharmacy Sales
Outbreak Detection --- New York City,
August 2001--September 2003
Debjani Das,F. Mostashari, D. Weiss, S. Balter, R. Heffernan
New York City Department of Health and Mental Hygiene, New York, New York
Corresponding author: Debjani Das, New York City Department of Health and Mental Hygiene, 125 Worth Street, Room 318, CN#22A, New York, NY 10013. E-mail:
Introduction: Because over-the-counter medications (OTCs) are commonly taken before patients seek medical
care, OTC sales data might serve as an early indicator of communitywide illness. Since August 2002, the New York City Department of Health and Mental Hygiene (DOHMH) has tracked OTC sales from New York City pharmacies
to enhance detection of natural and intentional infectious disease outbreaks.
Objectives: First-year surveillance results on OTC sales were summarized and compared with results from
an emergency department (ED) syndromic surveillance system.
Methods: A file containing the number of OTC units sold the previous day, by drug name and retail store,
is transmitted to DOHMH daily from a central pharmacy database. The influenza-like illness (ILI) drug
category includes cough and influenza medications whose sales correlate strongly with annual influenza epidemics. The antidiarrheal drug category includes generic and brand-name loperamide. Citywide trends are evaluated by using
a linear regression model, controlling for seasonality, day of week, promotional sales, and temperature and
are compared with ED data. Spatial clustering by store is evaluated by using the spatial scan statistic
(SaTScan software, available at
Results: Citywide ILI drug sales were highest during annual influenza epidemics and elevated during the spring
and fall allergy seasons, similar to trends in the ED system (Figure). Loperamide sales peaked during influenza season
but did not increase substantially during the November 2002 viral gastroenteritis season. A spike in
loperamide sales occurred after the August 2003 New York City blackout. Spatial signals for ILI sales occurred on 277 of 365 days.
Conclusions: The effect of allergies and asthma on respiratory illness should be considered when interpreting trends
in OTC sales for ILI. Loperamide sales were not a useful indicator of a large 2002 norovirus outbreak
detected by ED surveillance. Spatial cluster analysis was sensitive to variability in sales data by store and has not proven useful. OTC sales indicate correlation with other syndromic surveillance
systems, but methods require refinement.
Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of
Health and Human Services.References to non-CDC sites on the Internet are
provided as a service to MMWR readers and do not constitute or imply
endorsement of these organizations or their programs by CDC or the U.S.
Department of Health and Human Services. CDC is not responsible for the content
of pages found at these sites. URL addresses listed in MMWR were current as of
the date of publication.
All MMWR HTML versions of articles are electronic conversions from ASCII text
into HTML. This conversion may have resulted in character translation or format errors in the HTML version.
Users should not rely on this HTML document, but are referred to the electronic PDF version and/or
the original MMWR paper copy for the official text, figures, and tables.
An original paper copy of this issue can be obtained from the Superintendent of Documents,
U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800.
Contact GPO for current prices.
**Questions or messages regarding errors in formatting should be addressed to