Three weeks after an apparent foodborne illness outbreak at the Cass County Jail, the North Dakota Department of Health determined what likely made about 110 inmates sick over a two-day stretch in mid-December.

Although an official cause is still pending, State Epidemiologist Laura Cronquist says testing by the U.S. Centers for Disease Control and Prevention points to Clostridium perfringens bacteria as the culprit, based on stool samples from several inmates.

Clostridium perfringens is commonly found on raw meat and poultry, according to the CDC, and infection can occur when foods are prepared in large quantities and kept warm for a long time before serving.

“It’s really common,” Cronquist said, adding, “It’s not really surprising that it’s an institution that this happened in.”

Last month’s outbreak was the second major outbreak at the Cass County Jail in four years. In the latest case, about 40 percent of the jail’s 282 inmates had symptoms including diarrhea and nausea. No inmates were hospitalized, and jail staff said the illness was short-lived.

Clostridium perfringens was also the likely cause of a larger illness outbreak at the jail in November 2011, when 90 percent of the 184 inmates inmates came down with diarrhea and vomiting. In that case, the organism was also found inside sick inmates, but couldn’t be confirmed in the most likely food source, the chili macaroni served that day.

The Cass County Jail freezes meal samples daily to save in the event of illness in a process referred to in the corrections industry as a “dead man’s tray.” Cronquist said she’s working with the CDC to determine which of those specific foods will be tested.