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Multistate Outbreak of Human Salmonella I 4,[5],12:i:-Infections Associated with Frozen Rodents (Final Update)

Posted August 2, 2010

This outbreak appears to be over. However, Salmonella is an important cause of human illness in the United States. More information about Salmonella, and steps people can take to reduce their risk of infection, can be found on the CDC Salmonella Web Page.


Persons Infected with the Outbreak Strain of Salmonella I 4,[5],12:i:-, United States, by State
Infections with the Outbreak Strain of Salmonella I 4,[5],12:i:-, by Date of Illness Onset

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 infection, serotype I 4,[5],12:i:-. 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 9pm EDT on July 29, 2010, a total of 34 individuals infected with a matching strain of Salmonella serotype I 4,[5],12:i:- have been reported from 17 states since January 1, 2010. The number of ill persons identified in each state with this strain is as follows: AL (1), AZ (1), CO (1), GA (7), IA (1), IL (3), MA (3), MI (1), MO (3), NC (3), NV (1), NY (2), SC (1), TN (1), VA (1), WI (3), and WY (1).

Among the persons with reported illness onset dates available, illnesses began between December 4, 2009, and June 9, 2010. Infected individuals range in age from <1 to 57 years old and the median age is 12 years. Fifty-three percent of patients are male. Among the 17 patients with available information, 1 (6%) was hospitalized. As of July 29, 2010, no deaths attributed to this infection have been reported.

The outbreak can be visually described with a chart showing the number of persons who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after June 14, 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. Please see the Salmonella Outbreak Investigations: Timeline for Reporting Cases for more details.

Investigation of the Outbreak

CDC and public health officials in multiple states are conducting an epidemiologic study. Preliminary analysis of this study has suggested an association with frozen rodents used for reptile feed. Ill persons (61 percent) were significantly more likely than well persons (0 percent) to report any exposure to rodents in the week before illness. Additionally, ill persons (26 percent) were significantly more likely than well persons (0 percent) to report using frozen rodents for reptile feed in the week before illness. An environmental investigation was conducted by the FDA, and culture of samples collected yielded Salmonella that matched the human outbreak strain.

Although referred to differently in the United States and United Kingdom, the strain in the U.S. investigation is indistinguishable from the strain that caused an outbreak in the United Kingdom in 2009. The outbreak investigation by the Health Protection Agency of the United Kingdom implicated frozen mice imported from the United States as food for pet reptiles as the source of human illness.

On July 23, 2010, the company producing the frozen rodents announced a recall.

CDC and state and local public health partners are continuing surveillance to identify new cases. We will update the public on the progress of this investigation as information becomes available.

Clinical Features/Signs and Symptoms

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.

More general information about Salmonella can be found here under Salmonella FAQs.

Reptiles can carry Salmonella for years without signs of illness. More information about reptiles and Salmonella can be found here.

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Advice to Consumers

  • Wash your hands thoroughly with soap and water immediately after handling frozen rodents used as food for reptiles, or anything in the area where they are stored, thawed, prepared, and fed to reptiles.
  • Wash your hands thoroughly with soap and water immediately after handling live rodents and reptiles, or anything in the area where they live and roam.
  • Running water and soap are best. Use hand sanitizers if running water and soap are not available. Be sure to wash your hands with soap and water as soon as a sink is available. Directions for washing hands can be found here.
  • Keep frozen rodents away from areas where food and drink are stored, prepared, served, or consumed.
  • Avoid using microwave ovens or kitchen utensils used for human food to thaw frozen rodents used for reptile feed. Any kitchen surfaces that come in contact with frozen rodents should be disinfected afterwards.
  • Do not let children younger than 5 years of age or people with weakened immune systems handle frozen rodents.
  • Use soap or a disinfectant to thoroughly clean any surfaces that have been in contact with frozen rodents. Children older than 5 years old should perform this task only under adult supervision.
  • Recalled frozen rodents used as food for reptiles may still be in stores and in consumers' homes, including in the freezer. Any recalled product should be thrown away to prevent Salmonella infections in humans, pets, or other animals. This product should be disposed of in a closed plastic bag and placed in a sealed trash can to prevent people or animals, including wild animals, from eating it.

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