A lsteria outbreak linked to sliced deli meats has killed two people and sickened 28 others across 12 states, according to the Centers for Disease Control and Prevention.

It is currently unknown what brands of deli meat are tied to the outbreak, but an active investigation aims to determine the specific products that may be contaminated, the agency said in an update Friday.

“Products sold at the deli, especially those sliced or prepared at the deli, can be contaminated with Listeria,” the CDC notes on its website. “Listeria spreads easily among deli equipment, surfaces, hands and food.”

The states currently impacted include: Georgia, Illinois, Maryland, Massachusetts, Minnesota, Missouri, New Jersey, New York, North Carolina, Pennsylvania, Virginia and Wisconsin.

What is listeria?

Listeria is a type of bacteria that can cause illness known as listeriosis. The CDC defines listeriosis as “a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes.”

It is especially harmful to people who are pregnant, elderly (aged 65 or older) or who have weakened immune systems. 

An estimated 1,600 people get listeriosis each year, and about 260 die, according to the agency.

To avoid illness, the CDC recommends people at higher risk avoid eating meats sliced at the deli or heat them to an internal temperature of 165°F or until steaming hot before eating. Refrigeration does not kill listeria.

The current outbreak has been linked to contaminated deli meat, but other types of food can also pose risks if they get contaminated with the bacteria, including unpasteurized raw milk or products made with it, or raw vegetables that had contact with listeria in the soil or fertilizer, the Mayo Clinic explains.

Symptoms of listeria infection

Signs and symptoms of listeria infection can vary. For intestinal illness, which usually starts within 24 hours after eating contaminated food and lasts around 1 to 3 days, symptoms include diarrhea and vomiting.

“This kind of illness is rarely diagnosed because laboratories do not regularly test patient stool (poop) samples for Listeria,” the CDC notes. But this can develop into invasive illness, which is when the bacteria spreads beyond the intestines.

Symptoms of invasive illness, or invasive listeriosis, generally start within 2 weeks after eating contaminated food. Symptoms for non-pregnant people include:

• Fever
• Flu-like symptoms, such as muscle aches and fatigue
• Headache
• Stiff neck
• Confusion
• Loss of balance
• Seizures

“Symptoms in non-pregnant people can be severe,” the CDC notes. “Almost 1 in 6 non-pregnant people with invasive listeriosis die.”

For pregnant people, symptoms also include fever and flu-like symptoms. While the symptoms are usually milder, and some pregnant people never even experience symptoms, the infection can harm the baby, leading to “miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn,” the CDC warns.