Oregon and Minnesota’s state health departments and departments of agriculture have again provided some of the critical epidemiological data in cracking the Salmonella outbreak linked yesterday to ConAgra’s Marie Calendar brand cheesy chicken and rice frozen entrees.  There are only two recognized illnesses in each state, but Minnesota generated the positive test result for Salmonella Chester on the recalled product. 

The CDC’s statement today on the outbreak states as follows:

CDC is collaborating with public health officials in many states, the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA/FSIS), and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Salmonella serotype Chester infections. Investigators are using DNA analysis of Salmonella bacteria obtained through diagnostic testing to identify cases of illness that may be part of this outbreak.

As of 9:00 AM EDT on June 18, 2010, a total of 30 individuals infected with a matching strain of Salmonella Chester have been reported from 15 states since April 11, 2010. The number of ill people identified in each state with this strain is as follows: CA (4), CO (2), GA (6), IL (1), KY (1), MA (2), MN (2), MO (1), NC (1), OK (1), OR (2), SC (2), TN (1), UT (1), and VA (3). 

The CDC’s description of the outbreak so far:

Beginning on June 14, 2010, CDC and public health officials in multiple states began conducting an epidemiologic study by comparing foods eaten by ill and well persons. As of June 18, information had been collected on 14 ill and 21 well persons. Preliminary analysis of this study suggests eating a Marie Callender’s frozen meal as a possible source of illness. Ill persons (86 percent) were significantly more likely than well persons (10 percent) to report eating a frozen meal. All ill persons (100 percent) who ate frozen meals reported eating a Marie Callender’s frozen meal. None (0 percent) of the well persons who ate a frozen meal reported eating a Marie Callender’s frozen meal. At this time there are insufficient data to implicate a specific frozen meal type. However, many of the ill persons have reported eating a Marie Callender’s cheesy chicken and rice frozen entrée in the week before becoming ill.

Today, the Minnesota Department of Agriculture Laboratory reported to CDC that it has isolated Salmonella Chester from an unopened package of Marie Callender’s Cheesy Chicken & Rice single-serve frozen entrée collected from a case patient. Subtyping of the Salmonella strain is under way.

ConAgra needs to help get the message out to their customers.  In addition to illnesses that happen before an outbreak is announced, another major public health concern is illnesses that have yet to happen, especially when the contaminated product is a frozen item that might stay in a freezer for months.  Below is a chart from another ConAgra outbreak; again linked to a frozen food product, pot pies.  It shows how many people became ill after the outbreak was announced.