CDC is collaborating with public health officials in multiple states, the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture's Food Safety and Inspection Service (USDA/FSIS) to investigate two multistate outbreaks of Salmonella infections, each involving a different Salmonella serotype: Hartford and Baildon. Both of these Salmonella serotypes are rare, and ill persons in both outbreaks have a similar age and geographic distribution. Investigators are using DNA analysis of Salmonella bacteria obtained through diagnostic testing to identify cases of illness that may be part of these outbreaks.
Epidemiologic studies comparing foods eaten by ill and well persons were conducted for both of these multistate outbreaks. In each study, analysis indicates that eating at a Mexican-style fast food restaurant chain, Restaurant Chain A, is associated with some illnesses. Among persons eating at Restaurant Chain A, no specific food item or ingredient was found to be associated with illness for either outbreak. The numbers of new cases for the Salmonella Hartford outbreak have declined substantially since a peak in early June 2010. The numbers of new cases for the Salmonella Baildon outbreak have declined substantially since a peak in late June 2010. The number of new cases of illness associated with these outbreak strains appears to have returned to baseline, indicating the outbreaks are not ongoing.
In both outbreaks, the FDA worked with CDC and state partners to conduct a traceback investigation. The tracebacks focused on produce that ill individuals reported eating and that had been implicated in previous outbreaks of salmonellosis. The extensive traceback effort was initiated to determine if a common source or supplier could be identified to help focus the epidemiologic investigations. No common food source was identified in either traceback. The FDA also sampled and tested produce items and did not find either outbreak strain. As with previous outbreaks in which contaminated produce may be the factor, produce tracebacks present substantial challenges because of the short shelf life of the product and the industry's comingling of product from multiple sources.
A widely distributed contaminated food product might cause illnesses in a specific region and across the United States. Although neither outbreak appears to be ongoing, indicating no continued risk of infection from this source, CDC and its public health partners are continuing their efforts to identify the specific contaminated product or products that caused illness and will update the public on the progress of this investigation as information becomes available.