Salmonella is a bacteria that can grow in soil, raw meats, insects, and water. It is a common cause of food poisoning. It can infect food at farms, in processing plants, or in the kitchen. Once eaten it can cause nausea, vomiting, abdominal cramps, diarrhea, and fever. While it usually goes away on its own in a couple of days it can cause serious problems in certain populations.
The US Centers for Disease Control and Prevention and state health agencies are responsible for tracking foodborne illnesses and finding the cause. An investigation started in late November when a growing cluster of people had become infected with a similar strain of Salmonella typhimurium. Three studies were done to help track the source to a processing plant.
From September 2008 to January 2009, 529 people from 43 states were infected with the strain. Out of that group 116 patients were hospitalized, and the strain may be linked to eight deaths. The link to peanut butter was found through three studies.
A case study of infected individuals helped identify the type of food that was more commonly consumed in this group than the general population. Out of 300 food items, the most significant difference was in peanut butter:
In the next step a case-control study was conducted. It involved 70 of the people affected and 178 controls that had not been sick. This study found that:
Outbreak clusters began to occur in institutions. Investigators found the culprit strain in an unopen jar of peanut butter. The peanut butter was traced back to one specific plant. The plant only sold to institutions or food manufacturers but not all illnesses were in institutional settings.
As a result a third case-control study was done to determine if other peanut butter products were also involved. In this study, 93 cases of infection were compared to 399 controls. The results found that:
The products affected have been found. The US Food and Drug Administration (FDA) has a full list of recalled products on their website, listed below. It is best to avoid these products until they are cleared. In most cases a salmonella infection will go away on its own in a few days. If your symptoms are severe contact your doctor. You may need IV fluid to help rehydrate you.
FDA—List of Recalled Peanut Products
Multistate outbreak of salmonella infections associated with peanut butter and peanut butter containing products. United States, 2008-2009.MMWR. January 29, 2009. 58 (Early Release);1-6.
Last reviewed February 2009 by Larissa J. Lucas, MD