Prisoners at several correctional institutions across Ontario may have been exposed to listeria, health officials are warning.

The operator of Eurest Dining Services, which produces and supplies food to Ontario correctional facilities, informed the Halton Regional Health Department on Friday that samples taken during routine surveillance at its food-production facility had tested positive for Listeria monocytogenes.

The positive tests are connected to food that may have been consumed between Nov. 13 and Nov. 16 at seven Ontario facilities:

  • Maplehurst and the Vanier Centre for Women in Milton.
  • Central North Correctional Centre in Penetanguishene.
  • Central East Correctional Centre in Lindsay.
  • Ottawa-Carleton Correctional Centre.
  • St. Lawrence Valley Correctional and Treatment Centre and the Brockville Jail in Brockville.

So far, there have been no reported cases of listeriosis among prisoners.

"Although there have been no cases, I am asking individuals who were present at these seven correctional institutions between the dates of Nov. 13 and 16, 2008 to seek medical attention if they develop symptoms of listeriosis," said Dr. David Williams, the province's acting chief medical officer of health, said in a news release Saturday.

 "There is no risk to the general public, and we are taking every possible step to notify individuals who may have been affected."

Some of the prisoners who were incarcerated during that period have since been released.

Health-care providers have been asked to watch for individuals linked with these correctional facilities who show symptoms of listeriosis.

The Halton Region Health Department has ordered Eurest Dining Services to cease production and distribution of food from the facility and immediately prepare and implement a plan to sanitize the plant and equipment, the statement said.

Listeria monocytogenes can be found in unpasteurized dairy products, raw vegetables and meats, and processed foods including deli meats and hot dogs. Ingesting the bacteria can cause serious illness including brain and blood infections that can lead to death.

The elderly, infants and people with compromised immune systems are the most vulnerable.

Some of the flu-like symptoms of listeriosis are nausea, vomiting, diarrhea, severe headaches, stiff neck and fever. It can take up to 70 days for symptoms to appear after the contaminated food is consumed.

Twenty people have died in connection with a listeria outbreak that became public in August, while approximately 4,000 became ill from consuming tainted meat.