STEVE INSKEEP, host:
Here's some of the story behind a warning we heard this week. It's the news of a salmonella outbreak that sickened almost 300 people and came from an unexpected source.
NPR's Allison Aubrey reports on how investigators tried to find that source.
ALLISON AUBREY: When investigators at the CDC and state health agencies first began to notice a trickle of salmonella cases last fall, they suspected raw meat, eggs, or other food that's more commonly tainted.
Dr. TIM JONES (Tennessee Department of Health): Peanut butter I think has surprised everybody and certainly was not on the top of our list of suspects.
AUBREY: Dr. Tim Jones of the Tennessee Department of Health was among the first to document cases of food poisoning in his state linked to a rare type of salmonella. And he reported the cases to PulseNet, the CDC's electronic tracking system for food-borne illnesses.
CDC investigator, Anandi Sheth, says when similar reports started coming in from all over the country, they decided to interview all the people who had gotten sick.
Dr. ANANDI SHETH (CDC Investigator): We asked them about 200 foods that they ate. And of those foods, peanut butter stood out as the food that was commonly eaten by most of the people who were ill.
AUBREY: By the time the CDC conducted enough interviews to name peanut butter as the real suspect, it was already January and people's memories about what they'd eaten months earlier when they got sick were a little shaky. So investigators like Tim Jones remained a little skeptical.
Dr. JONES: Everybody eats peanut butter. And so, to tell us that's like saying, yeah, I eat bread and drink milk. And so really the culprit did not become clear until we really got down to the level of what brand.
AUBREY: This is when investigators asked the people who had gotten sick to open up their cabinets to see if the jar of peanut butter they'd eaten back in the fall was still there.
Dr. JONES: A surprising number of people still have the actual jars around and were able to look at the numbers.
AUBREY: On the lids of the jars that tell where the peanut butter was made. This is how investigators narrowed the outbreak to jars of Peter Pan and Great Value brands of peanut butter made at a processing facility in Georgia. The plant is owned by ConAgra Foods, which has now recalled all jars of peanut butter that are labeled with product code 2111 from those two brands.
A spokesman for the company told NPR that everyday the plant inspectors randomly pull 60 to 80 jars of peanut butter and test them for salmonella. The company says they haven't had any positive hits for salmonella since at least 2004. Food scientists say the stuff means the salmonella wasn't present.
Ms. MARY WEAVER (National Sanitation Foundation): They're really looking for a very small needle in a large haystack when they're doing the testing after processing.
AUBREY: Food scientist Mary Weaver manages certifications for the National Sanitation Foundation. She says an outbreak of salmonella linked to peanut butter make come as a shock to consumers, but it's actually happened once before.
Back in 1996, in Australia, an outbreak made 54 people sick. In that case, they were able to figure where the salmonella came from.
Ms. WEAVER: They implicated actually the roasted peanuts that were used to make the peanut butter.
AUBREY: The roasting process usually kills off unwanted bacteria. But in that instance it seems the salmonella cells survived. In this new outbreak it's unclear whether the peanuts were tainted. Another possibility is that the Salmonella came through cross-contamination in the plant. The FDA has just begun its investigation.
The good news is that sickness from salmonella is rarely deadly. It can make people miserable for four to five days, but most people recover fully.
Allison Aubrey, NPR News, Washington.
INSKEEP: As you can imagine, that investigation caused a lot of concern. ConAgra's hotline was swamped with so many calls after the recall was announced on Wednesday that many people got a busy signal.
School officials in Houston confiscated students' sandwiches from home and replaced them with sandwiches made at the school. And in Georgia, a lawmaker representing one of the nation's biggest peanut-producing areas warned colleagues to throw out jars of peanut butter that he had recently handed out.