There have been two studies that have analyzed sales of diarrhea remedies during outbreaks of diarrheal diseases other than cryptosporidiosis (Edge et al., 2004, Angulo et al., 1997).
Edge and colleagues studied sales of diarrhea remedies during an outbreak of diarrhea in Walkerton, Ontario caused by contamination of the city's water supply with the bacterium E. coli O157:H7 (Edge et al., 2004). They found that weekly counts of sales of diarrhea remedies at one pharmacy increased twofold coincident with the rapid rise in cases as reflected by the epidemic curve for the outbreak. They found that the increase in OTC sales preceded an increase in emergency department visits for gastrointestinal illness. They used the detection-algorithm method to study the date that the outbreaks would have been detected by routine monitoring. The two detection algorithms that they studied both alarmed on weekly sales counts for the week ending May 26. The local health department had issued a boil-water advisory on May 21. Their study used a false alarm rate of one per year. They did not determine the false alarm rate at which a detection system using these algorithms would have detected the outbreak on the week ending May 19.
Angulo et al. (1997) studied a waterborne outbreak due to contamination of the water supply of the city of Gideon MO with Salmonella typhimurium. They found that sales of diarrhea remedies increased 600% during the outbreak relative to historical sales levels. The increase occurred in early December 1993 before health authorities issued a boil-water advisory on December 18. The paper does not provide details about the sales data they collected (number of pharmacies, weekly vs. daily counts, and specific dates of significant increase), and we mention this study for completeness.
Das et al. (2005) performed a correlation analysis of OTC diarrhea remedies in New York City. They found a poor correlation between sales of OTC diarrhea remedies and ED visits for diarrhea, with an r2 of 0.24. However, they did find an increase in sales of OTC diarrhea remedies during known outbreaks of gastrointestinal illness due to norovirus. They also noted an increase in sales of OTC diarrhea remedies during the electrical blackout that occurred in New York City in August 2003, suggesting that loss of refrigeration during the blackout led to contamination of food and a subsequent increase in gastrointestinal illness.
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