In the outbreak linked to ground beef sold at Hannaford Supermarkets, 16 people in seven states have now been infected with an antibiotic-resistant strain of Salmonella Typhimurium linked, the Centers for Disease Control and Prevention reported Tuesday.

At least seven of those people have been hospitalized, according to the CDC’s first report on the outbreak.  The antibiotic resistance of the pathogen may “be associated with an increase in the risk of hospitalization or possible treatement failure,” the CDC noted.

The ill people range in age from one to 79 years, with a median age of 45.  Cases in which the onset of illness occurred after Nov. 19 might not yet be counted, the CDC said, because it can take an average of two to three weeks between when a person becomes ill and when the illness is reported.

Maine, New Hampshire and New York each reported four cases associated with the outbreak, while single cases of outbreak-related Salmonella infection were reported by Hawaii, Kentucky, Massachusetts and Vermont. 

The link to Hannaford Supermarkets ground beef is so far based on epidemiologic and traceback evidence. The CDC said 11 of the 16 infected people reported eating ground beef in the week before they became ill. Ten of those 11 said they purchased the meat from Hannaford stores, generally between Oct. 12 and Nov. 20, 2011.

Hannaford, a chain based in Scarborough, ME, recalled an undetermined amount of fresh ground beef on Dec. 15. The recalled packages have sell-by dates of Dec. 17 or earlier.  Some of the recalled ground beef could still be in freezers, and the CDC advised consumers and restaurant and food service operators not to serve it.

The outbreak investigation, which involves the CDC, the USDA’s Food Safety and Inspection Service and their state partners, is continuing.  The CDC said representatives from Hannaford Supermarkets have been cooperating with public health officials throughout the investigation.

CDC Outbreak Map: