Investigators found the drug-resistant salmonella virus Heidelberg in 4 samples of turkey during a routine check of retail stores in the United States. The U.S. Centers for Disease Control and Prevention has decided to not yet release the stores in which the tainted meat was found, and no recall has been issued.

ABC News reports:

The reason for the lack of a recall is that the strain is not technically considered an “adulterant” — in other words, screeners finding it on meat in a grocery store is not enough to trigger a recall.

The CDC has found specific brands of turkey at stores with this strain of salmonella. And hospitals and doctors have found 77 people sickened by the same strain. But investigators have been unable to directly link an ill person to the brand of turkey that made them sick.

When asked why the USDA has not yet released the name of any establishments, Neil Gaffney, press officer for the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) said, “Despite an extensive investigation by FSIS and CDC, there is very little epidemiological information available at this time that directly links these illnesses to any specific product or establishment. Without this direct link and without specific enough data, it would not be appropriate to issue a recall notice.

“FSIS is committed to continuing this investigation in order to obtain the additional information necessary to find the source of this outbreak, and take appropriate action to protect public health,” Gaffney said.

The Center for Science in the Public Interest petitioned the USDA in May to declare this strain of salmonella an adulterant.

The outbreak began in March 2011 when the CDC and the FSIS received reports of a number of cases of an antibiotic-resistant strain of salmonella that is often difficult to treat. To date Michigan, Ohio, Texas, Illinois, California and Pennsylvania have been most affected by the outbreak. Twenty-two people have been hospitalized.

Public health investigators are currently using DNA “fingerprints” of this bacteria in order to identify cases of illness. Though a public health warning concerning the outbreak was issued on July 29 by the FSIS, and the CDC has matched this particular strain of bacteria to four contaminated ground turkey products, there is reportedly not enough information to issue an official recall at this time.

Salmonella poisoning usually results in diarrhea, fever and stomach cramps during the 12 to 72 hours after a contaminated item is consumed, and symptoms will last for four to seven days, according to the CDC. Most people recover without treatment, but in some — especially those with weakened immune systems such as the elderly, small children and people with HIV/AIDS — severe illness and even death can result.

Because the salmonella Heidelberg strain is antibiotic-resistant, those infected are more likely to require hospitalization, the CDC reports.