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). Among those for whom information is available about when symptoms started, illnesses began between April 5, 2010 and May 29, 2010. Case-patients range in age from <1 to 88 years old, and the median age is 37 years. Fifty-four percent of patients are female. Among the 15 patients with available hospitalization information, 6 (40%) were hospitalized. No deaths have been reported.
The outbreak can be visually described with a chart showing the number of people who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after May 22, 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.
A widely distributed contaminated food product might cause illnesses across the United States. The identity of the contaminated product often is not readily apparent. In outbreaks like this one, identification of the contaminated product requires conducting detailed standardized interviews with persons who were ill. It may also require conducting interviews with non-ill members of the public (“controls”) to get information about foods recently eaten and other exposures to compare with information from the ill persons. The investigation is often supplemented by laboratory testing of suspected products.
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.
This investigation is ongoing. CDC and state and local public health partners are continuing surveillance to identify new cases and identify the contaminated product or products that are causing illness. The CDC will update the public on the progress of this investigation as information becomes available.
Most persons infected with Salmonella develop diarrhea, fever, and abdominal cramps 12-72 hours after infection. Infection is usually diagnosed by culture of a stool sample. The illness usually lasts from 4 to 7 days. Although most people recover without treatment, severe infections may occur. Infants, elderly persons, and those with weakened immune systems are more likely than others to develop severe illness. When severe infection occurs, Salmonella may spread from the intestines to the bloodstream and then to other body sites and can cause death unless the person is treated promptly with antibiotics.