The grocery store membership card in your wallet could save your life! Because when there’s an outbreak of food poisoning, health departments are increasingly turning to loyalty cards to help locate tainted products and to use the cards to warn anyone who bought them.

Experts estimate that 48 million people get food-borne illnesses every year, and 3-thousand die. They point out that loyalty cards are incredibly helpful in an outbreak investigation, because 80 percent of us belong to at least one shopper rewards program. So, stores know exactly who bought what. And the information – which includes everything from lot numbers, to “use by” dates – can help quickly pinpoint the source of infection.

Loyalty cards allow investigators to remove tainted products from shelves faster giving doctors a better idea about the kind of bug they’re treating and allowing officials to warn customers who might not even have symptoms yet to get immediate medical attention.

The first time loyalty cards helped an investigation was during an outbreak of salmonella poisoning that sickened nearly 300 people in 44 states.

The CDC finally turned to Costco, and used their membership card information to trace the outbreak to a batch of pepper-crusted Italian meats. And now, Costco gets a couple of requests a month from the CDC.

Investigators say that loyalty card information is especially valuable because it can take several days for people to get sick. And a month before the problem is reported. And it’s much more accurate than asking people who are deathly sick to reconstruct what they think they bought and ate over the last month that made them sick.