Fourteen people have been sickened with Salmonella Infantis infections in a 9-state outbreak linked to dog food. At least five of the individuals have been hospitalized, according to the Centers for Disease Control and Prevention.

The CDC reported Thursday that multiple brands of Diamond Pet Foods dry dog food – including several that have been recalled in recent days – are the likely source of the human illnesses, either through contact with the contaminated food or through handling an animal that has eaten the tainted kibble. The dog food was produced at a single manufacturing plant in South Carolina.

How many dogs may also have been sickened was not mentioned in the CDC report. In some recall notices, Diamond Pet Foods has claimed that no dog illnesses have been reported. Those recall alerts from the company did not reveal that human cases of infection were being investigated.

According to the CDC, routine tests by the Michigan Department of Agriculture and Rural Development first detected Salmonella in an unopened bag of Diamond Pet Foods Naturals Lamb Meal & Rice dry dog food on April 2.

PulseNet, the national surveillance system for foodborne illnesses, then spotted several cases of human Salmonella Infantis infections with a genetic fingerprint identical to that found in the dog food, the CDC said.

The outbreak strain of Salmonella Infantis was isolated from an opened bag of Diamond Brand Chicken Soup for the Pet Lover’s Soul Adult Light Formula dry dog food, found in the household of an ill person in Ohio. The outbreak strain was also isolated in samples taken from an unopened bag of the dog food obtained from an Ohio retail store.

A sample of Diamond Puppy Formula dry dog food collected by the Food and Drug Administration during an inspection at the South Carolina production plant yielded Salmonella, the CDC said.

Seven of 10 outbreak victims interviewed said they had contact with a dog during the week before they became ill. Of five people who could remember the type of dog food they had handled, four said it was a Diamond Pet Foods brand.

Missouri and North Carolina each confirmed 3 cases related to the dog food outbreak. Ohio reported two cases while Alabama, Connecticut, Michigan, New Jersey , Pennsylvania and Virginia each reported single cases.

The first onset of human illness reported was Oct. 8, 2011 and the most recent illness onset was April 22 — more than two weeks after the first pet food recall. The case patients range in age from 1 to 82 years old with a median age of 48. Seventy-seven percent of the ill people are female.

Diamond Pet Foods recalled certain batches of its Naturals Lamb Meal & Rice dry dog food on April 6 as a “precautionary measure” and stated then that “no illnesses have been reported and no other Diamond manufactured products are affected.” That was four days after the Michigan test results.

Then a second recall was announced April 26 for certain production codes of Chicken Soup for the Pet Lover’s Soul Adult Light formula dry dog food. This time, the recall alert stated more narrowly that “no dog illnesses” had been reported.

On April 30, the company expanded the recall to include Diamond Puppy Formula dry dog food and again said there were no reports of dog illnesses related to the product. No mention was made of human infections in the recall announcement.

“There have been numerous human outbreaks linked to pet food,” said food safety attorney Bill Marler, managing partner at Marler Clark (publisher of Food Safety News). “It again shows how important food safety is, both to your pet and your family.”

According to the CDC, dogs and cats infected with Salmonella usually have diarrhea and may seem lethargic, but they also can carry the infection and not appear to be sick. Humans can become ill by touching infected animals, contaminated food, or objects and surfaces such as food bowls, especially if they do not thoroughly wash their hands after the contacts.

The CDC offered this advice for pet owners:

– Consumers should check their homes for recalled dog food products and discard them promptly. Consumers with questions about recalled dog food may contact Diamond Pet Foods at telephone number 800-442-0402 or visit www.diamondpetrecall.com.

– Follow the tips listed on Salmonella from Dry Pet Food and Treats to help prevent an infection with Salmonella from handling dry pet food and treats.

– People who think they might have become ill after contact with dry pet food or with an animal that has eaten dry pet food should consult their health care providers. Infants, older adults, and persons with impaired immune systems are more likely than others to develop severe illness.

– People who think their animal might have become ill after eating dry pet food should consult their veterinary-care providers.

Additional information for pet owners can be found here.

CDC Outbreak Map