British Columbia detectives seem to have found another benefit from grocery loyalty cards aside from earning discounts and points.

In early 2012, disease detectives used grocery loyalty cards to study the foods that people who were infected with hepatitis A bought in the past months. Through this investigation, they were able to identify the foods that were linked to the infection and stop an outbreak.

It usually takes a long time before health officials get to recognize that an outbreak of a food-borne disease is underway because of constrictions in geography and in the case of hepatitis A, people only start to see the symptoms from 15 to 50 days after contact with the infection. By then, the source could be difficult to trace because patients find it hard to specifically recall which foods they ate weeks before.

Through grocery loyalty cards, the detectives studied the food buying histories of the patients and found that the pomegranate seeds found in frozen fruit mixes were the source of the disease. They identified the specific brand of frozen fruit mix that the infected people purchased. The mix contained strawberries, blueberries, pomegranate seeds and cherries.

After several tests, the pomegranate seeds proved to be contaminated with the infection and were recalled. The loyalty cards made it easy to identify the source of infection early in the outbreak. Hepatitis is rare in British Columbia but people who travel in and return from other countries where the infection circulates can transmit it to people in the country.

Hepatitis A is caused by fecal transmission usually from contaminated water or food. The infection can cause mild to severe fever, fatigue, dark urine, abdominal pain and jaundice. It causes inflammation to the liver and sometimes can even result to failure of the liver.

"Hepatitis A won't kill you, but it will make you feel like you want to die," University of Southern California and Keck Medical Center professor Dr. Sharon Orrange said. "We can prevent the illness in people who have been exposed, but they must be vaccinated in the two-week period after exposure. If received within two weeks, the vaccine is up to 90 percent effective in preventing illness."