A listeria outbreak has resulted in three fatalities and one pregnancy loss, traced back to heat-and-eat chicken fettucine alfredo products recently recalled from Kroger and Walmart, according to federal health officials.

The outbreak, which includes at least 17 people in 13 states, began last August, officials said late Tuesday.

FreshRealm, a prominent food producer with locations in California, Georgia, and Indiana, has initiated a recall for items made prior to June 17. This recall applies to specific products distributed to retail stores:

– 32.8-ounce trays of Marketside Grilled Chicken Alfredo with Fettucine, featuring Tender Pasta with Creamy Alfredo Sauce, White Meat Chicken, and Shaved Parmesan Cheese, with best-by dates no later than June 27.

– 12.3-ounce trays of Marketside Grilled Chicken Alfredo with Fettucine Tender Pasta with Creamy Alfredo Sauce, White Meat Chicken, Broccoli and Shaved Parmesan Cheese with best-by dates of June 26 or earlier.

– 12.5-ounce trays of Home Chef Heat & Eat Chicken Fettucine Alfredo with Pasta, Grilled White Meat Chicken and Parmesan Cheese, with best-by dates of June 19 or earlier.

The strain of listeria bacteria tied to the outbreak has been detected in sick people from August through May, health officials said. The same strain that made people sick was found in a sample of chicken fettucine alfredo during a routine inspection in March. That product was destroyed and never sent to stores. Officials said they have not identified the specific source of the contamination.

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Officials with the U.S. Centers for Disease Control and Prevention said the agency is investigating the outbreak, and planned to release more details. It was not clear which states are involved or where the deaths and pregnancy loss occurred.

Consumers shouldn’t eat the products, which may be in their refrigerators or freezers. They should be thrown away or returned to place of purchase.

Listeria infections can cause serious illness, particularly in older adults, people with weakened immune systems and those who are pregnant or their newborns. Symptoms include fever, muscle aches, headache, stiff neck, confusion, loss of balance and convulsions.

About 1,600 people get sick each year from listeria infections and about 260 die, the CDC said. Federal officials in December said they were revamping protocols to prevent listeria infections after several high-profile outbreaks, including one linked to Boar’s Head deli meats that led to 10 deaths and more than 60 illnesses last year.