Is syndromic surveillance of OTC drug sales effective in detecting outbreaks of waterborne GI disease?

Reports following waterborne disease outbreaks such as the 1996 cryptosporidiosis outbreak in Milwaukee, Wisconsin, suggested that sales of over‐the‐counter (OTC) drugs could provide an early indication of waterborne disease. As a result, many health departments implemented syndromic surveillance of OTC drug sales. The authors evaluated the ability of OTC diarrheal remedy sales to predict gastrointestinal (GI) disease. No significant correlations were identified between weekly sales and case counts, outbreak counts, or number of outbreak‐associated cases. Signals generated by the medication sales model did not coincide with outbreak weeks more reliably than signals chosen randomly. Although not tested with large outbreaks, this work does not support the use of syndromic surveillance for GI disease with OTC remedy sales. Given study results and the lack of compelling evidence in the literature of an association between drug sales and diarrheal illness, water agencies and health authorities may want to focus on other potential monitoring activities for early indication of waterborne disease.