Public health officials are turning to a surprisingly effective tool in their efforts to track down bouts of salmonella and other food-borne illness outbreaks: the shopper loyalty card.
The widely used cards, introduced in 1987, allow epidemiologists to scan food purchases as they try to trace culprits in food illness episodes that seem to have no obvious links.
They "provide an accurate picture of a customer's food history," says Jeffrey Hammond, with the New York State Department of Health in Albany.
Privacy is a huge concern in using cards to track outbreaks, officials say. All health departments are required to get permission to use them, Hammond says. "This is voluntary: People are not required to consent to having the grocery chain release their shopper-card history," he says.
And not all stores will supply records, even with written consent, says Casey Barton Behravesh, with the Centers for Disease Control and Prevention.
But when granted access, officials have found it a valuable evidence trail.
Consider: An outbreak of salmonella in five Eastern states has sickened 42 people so far this year, with two hospitalizations.
Based on routine interviews, officials found a "red flag": that all the patients shopped at Wegmans, a supermarket chain, Behravesh says. Given permission by patients to check their shopper club card data, officials found "a lot of these people were buying bulk Turkish pine nuts," or foods that contained them, which were contaminated with salmonella, Behravesh says.
Other recent cases:
An outbreak of E. coli O157:H7 that sickened 33 people and led to 15 hospitalizations in five Western states in 2010 was quickly traced to raw milk Gouda cheese produced by Bravo Farms in Traver, Calif., using Costco purchasing data.
A puzzling outbreak of salmonella Montevideo that sickened 272 people in 44 states in 2009 was finally cracked when health officials examined shopper records from Costco and saw that almost everyone who had gotten sick had purchased salami from Daniele Inc. Testing showed it was not the sausage but the black and red pepper it was coated in that carried the bacteria.
"It's very helpful because it's very hard for people to remember what they ate a couple of days before, not to mention a couple of weeks ago," Behravesh says.
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