In May 2010, CDC identified a nationwide increase in the number of Salmonella Enteritidis isolates with PFGE pattern JEGXX01.0004 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. This increase is evident in the epidemic curve, or epi curve. During May 1 to July 31, 2010, a total of 1,953 illnesses were reported. However, 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 700 illnesses during this same period. Many states have reported increases of this pattern since May. 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. CDC is currently conducting testing using advanced molecular methodologies to help distinguish between outbreak-related cases and sporadic (or background) cases.
Illnesses that occurred after July 17, 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 takes an average of 2 to 3 weeks for Salmonella. For more details, please see the Salmonella Outbreak Investigations: Timeline for Reporting Cases.
Epidemiologic investigations conducted by public health officials in 10 states since April have identified 26 restaurants or events where more than one ill person with the outbreak strain has eaten. Data from these investigations suggest that shell eggs are a likely source of infections in many of these restaurants or events. Preliminary information indicates that Wright County Egg, in Galt, Iowa, was an egg supplier in 15 of these 26 restaurants or events. A formal traceback conducted by state partners in California, Colorado, and Minnesota, in collaboration with FDA and CDC, found that shell eggs from five of these restaurants or events were from a single firm, Wright County Egg in Galt, Iowa. FDA is currently conducting an extensive investigation at the firm in Iowa. The investigation includes CDC participation and involves sampling, records review and looking for potential sources of contamination, such as feed. The investigation continues and updates will be made available.
According to the CDC, for every one person who is a stool-culture confirmed positive victim of salmonella in the United States, there a multiple of 38.5 who are also sick, but remain uncounted. (See, AC Voetsch, “FoodNet estimate of the burden of illness caused by nontyphoidal Salmonella infections in the United States,” Clinical Infectious Diseases 2004; 38 (Suppl 3): S127-34).
That would be 1,953 – 700 = 1,253 x 38.5 = 48,240.5