Multistate outbreak of Salmonella serotype Bovismorbificans infections associated with hummus and tahini–United States, 2011

On September 27, 2011, three clinical isolates of Salmonella enterica serotype Bovismorbificans with indistinguishable pulsed-field gel electrophoresis (PFGE) patterns were identified by the District of Columbia Public Health Laboratory (PHL). Human infection with S. Bovismorbificans is rare in the United States. Through query of PulseNet, the national molecular subtyping network for foodborne disease surveillance, six additional cases with indistinguishable PFGE patterns were identified in three states (Maryland, Michigan, and Virginia) during the prior 60 days. All nine patients had eaten at restaurants in the District of Columbia (DC) or northern Virginia <2 weeks before illness onset. This report summarizes the investigation led by the DC Department of Health (DOH), in which 23 cases of S. Bovismorbificans infections were identified among persons from seven states and DC, with illness onset during August 19-November 21, 2011. On May 30, 2012, traceback indicated that contaminated tahini (sesame seed paste) used in hummus prepared at a Mediterranean-style restaurant in DC was a plausible source of Salmonella infections. DOH restricted the sale of hummus and prohibited the use of hummus ingredients in other food items at implicated restaurants to prevent further illness. This investigation also illustrates challenges associated with ingredient-driven outbreaks and the value of PulseNet for identifying clusters of cases that are geographically dispersed.