Investigation Update: Multistate Outbreak of Human Salmonella Enteritidis Infections Associated with Shell Eggs

Number of Salmonella Enteritidis cases matching PFGE pattern JEGX01.0004 reported to PulseNet, United States, 2010

In July 2010, CDC identified a nationwide sustained increase in the number of Salmonella Enteritidis isolates with PFGE pattern JEGX01.0004 uploaded to PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections. An increase in reports beginning in May, peaking in July, and returning to baseline in November, is evident in the epidemic curve, or epi curve. From May 1 to November 30, 2010, a total of 3,578 illnesses were reported. However, some cases from this period may not have been reported yet, and some of these cases may not be related to this outbreak. Based on the previous 5 years of reports to PulseNet, we would expect approximately 1,639 total illnesses to occur during this same period. This means there are approximately 1,939 reported illnesses that are likely to be associated with this outbreak. Because of the large number of expected cases during this period, standard methods of molecular subtyping alone are not sufficient to determine which reported cases might be outbreak-associated.

Human Salmonella Enteritidis infections that occurred after October 28, 2010 might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This typically takes two to three weeks for Salmonella, but can take up to six weeks. For more details, please see the Salmonella Outbreak Investigations: Timeline for Reporting Cases.