Since May 2010, the Centers for Disease Control and Prevention, Atlanta, has identified a nationwide, four-fold increase in the number of S.E. isolates through PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories. The C.D.C. received reports of approximately 200 S.E. cases every week during late June and early July. Normally, the C.D.C. has received an average of some 50 reports of S.E. illness each week for the past five years. Many states also have reported increases of this pattern since May 2010, according to the agency.
Epidemiologic investigations conducted by public health officials in California, Colorado and Minnesota have revealed several restaurants or events where more than one person ill with this type of S.E. has eaten.
The F.D.A. and the C.D.C. conducted a traceback investigation and found many of the restaurants received shell eggs from Wright County Egg of Galt, Iowa. The company initiated a recall on August 13 and later expanded the recall on Aug. 18.