COPENHAGEN, Denmark – A Listeria outbreak associated with contaminated sausage may have killed 12 people over a few months, according to State Serum Institute (SSI), an infectious disease research institute under Denmark's state health ministry.

Danish food-safety authorities traced at least 20 illnesses to Danish rullepølse, or “rolled sausage”. Rullepølse is made from flattened pork belly spread with herbs and seasoning and then rolled up and sliced as a deli product. Jørn A. Rullepølser A/S in Hedehusene, Denmark manufactured the contaminated rullepølse. SSI said illnesses date back to September 2013. Genome sequencing of Listeria bacteria collected from infected individuals revealed the 20 victims were infected with the same bacteria.

“DVFA has today [Aug. 12] closed the company that has produced the sausage roll, as new samples from the company were positive for Listeria,” SSI said in a statement. “In addition, we launched a full withdrawal of the company’s products, which include meat products and sausages.”

The patients in the outbreak include 11 women and nine men aged 43-89 years, SSI noted. Twelve infected individuals died within 30 days after the test date. SSI said that in past Listeria outbreaks, patients have had serious underlying disease, and public health officials couldn't attribute Listeria as the sole cause of death.