At least two people in Rhode Island have developed infections from Listeria monocytogenes, causing public health officials to warn against eating soft cheese referred to as queso fresco.

An alert posted Wednesday by the Rhode Island Department of Health did not include any details about the two victims, but specifically urged pregnant women to not eat cheese made with unpasteurized milk. Pasteurizing milk kills Listeria and other bacteria that often are present in so-called raw milk.

“Queso fresco is a type of soft cheese. Queso fresco, queso blanco, panela, and asadero-style cheeses are only considered safe when they are marked with a professional label stating that they are ‘pasteurized’ or ‘made from pasteurized milk,’ ” according to the state warning.

“Homemade queso fresco is sometimes made with unpasteurized, or raw, milk. Unpasteurized milk can cause serious illness.”

Pregnant women are significantly more likely than other people to develop serious listeriosis infections when they consume foods or beverages contaminated with even trace amounts of the bacteria.

Among pregnant women, the highest rates of listeria are seen among Hispanic women, according to the Rhode Island health warning. A pregnant woman with listeriosis can pass the infection to her unborn baby. It can cause miscarriages, stillbirths, and impairments in newborns.

Anyone who has eaten any soft cheese recently and developed symptoms of Listeria infection should seek medical attention and tell their doctors about the possible exposure. It can take up to 70 days after exposure to the bacteria for symptoms to develop.

Symptoms can include fever, muscle aches, headache, stiff neck, confusion, loss of balance and convulsions sometimes preceded by diarrhea or other gastrointestinal symptoms. In some cases an invasive infection spreads beyond the gastrointestinal tract.

In addition to pregnant women, high-risk groups include young children, older adults and people with weakened immune systems, including cancer patients and transplant recipients.

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