Salmonella

Investigation of a Multistate Outbreak of Human Salmonella I 4,[5],12:i:- Infections Linked to Alfalfa Sprouts

December 23, 2010

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Introduction

CDC is collaborating with public health officials in many states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Salmonella serotype I 4,[5],12:i:- 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.

From November 1 to December 21, 2010, a total of 89 individuals with a matching strain of Salmonella serotype I 4,[5],12:i:- have been reported from 15 states and the District of Columbia. The number of ill people identified in each state with the outbreak strain is as follows: Connecticut (1), District of Columbia (1), Georgia (1), Hawaii (1), Iowa (1), Illinois (50), Indiana (9), Massachusetts (1), Missouri (14), New York (1), Pennsylvania (2), South Dakota (1), Tennessee (1), Texas (1), Virginia (1), and Wisconsin (3). Among 81 persons for whom information is available, illness onset dates range from November 1 to December 14, 2010. Case-patients range in age from 1 to 75 years, with a median age of 28. Sixty-eight percent of patients are female. Among persons with available information, 23% reported being hospitalized. No deaths have been reported. Because the pulsed-field gel electrophoresis (PFGE) pattern associated with this particular Salmonella serotype commonly occurs in the United States, some of the cases identified may not be related to this outbreak.

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 December 2, 2010, might not be reported yet 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 more details, please see Salmonella Outbreak Investigations: Timeline for Reporting Cases.

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Investigation of the Outbreak

Public health officials in multiple states have been interviewing ill persons to obtain information regarding foods they might have eaten and other exposures in the week prior to illness. Preliminary results of this investigation indicate a link to eating alfalfa sprouts at a national sandwich chain.

This investigation is ongoing. CDC, FDA, and state and local public health partners are continuing surveillance to identify new cases and trace potentially contaminated product. CDC will update the public on the progress of this investigation as information becomes available.

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Clinical Features/Signs and Symptoms

Most persons infected with Salmonella develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. The illness usually lasts 4 to 7 days, and most persons recover without treatment. However, in some persons, the diarrhea may be so severe that the patient needs to be hospitalized. Salmonella infection may spread from the intestines to the blood stream, and then to other body sites and can cause death unless the person is treated promptly with antibiotics. The elderly, infants, and those with impaired immune systems are more likely to have a severe illness from Salmonella infection.

Advice to Consumers

Persons who think they might have become ill from eating a potentially contaminated product should consult their health care providers. Since 1996, there have been at least 30 reported outbreaks of foodborne illness associated with different types of raw and lightly cooked sprouts. Most of these outbreaks were caused by Salmonella and E. coli.

To reduce the risk of illness:

Children, the elderly, pregnant women, and persons with weakened immune systems should avoid eating raw sprouts of any kind (including alfalfa, clover, radish, and mung bean sprouts).
Cook sprouts thoroughly to reduce the risk of illness. Cooking kills the harmful bacteria.
Request that raw sprouts not be added to your food. If you purchase a sandwich or salad at a restaurant or delicatessen, check to make sure that raw sprouts have not been added.

For more information on illnesses associated with sprouts, visit Foodsafety.gov.

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Additional Resources

CDC's Role in Food Safety

As an agency within the U.S. Department of Health and Human Services (HHS), CDC leads federal efforts to gather data on foodborne illnesses, investigate foodborne illnesses and outbreaks, and monitor the effectiveness of prevention and control efforts. CDC is not a food safety regulatory agency but works closely with the food safety regulatory agencies, in particular, with HHS’s Food and Drug Administration (FDA) and the Food Safety and Inspection Service within the U.S. Department of Agriculture. CDC also plays a key role in building state and local health department epidemiology, laboratory, and environmental health capacity to support foodborne disease surveillance and outbreak response. Notably, CDC data can be used to help document the effectiveness of regulatory interventions.

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