CDC Warns Pregnant People About Listeria Outbreak

If you are pregnant, your healthcare provider has likely given you a list of foods and drinks to avoid during pregnancy. In addition to limiting alcohol and avoiding raw fish, they probably have told you to refrain from eating cold deli meats, hot dogs, as well as pâtés and cheeses sold at the deli. This is because these foods are known sources of listeria—which can be particularly dangerous for pregnant people.

The Centers for Disease Control and Prevention (CDC) is currently tracking a deadly outbreak of listeria linked specifically to deli meats and cheeses. Consequently, they are warning pregnant people—as well as the elderly and those with weakened immune systems—that they are at higher risk for severe illness.

They recommend not eating meat and cheese directly from the deli counter, unless it has been heated to an internal temperature of 165 degrees Fahrenheit or until it is "steaming hot."

Listeria Outbreak Linked to Deli Meat

According to the CDC, six states have been impacted by the listeria outbreak, with 16 people getting sick. Thirteen people have been hospitalized and one person has died. However, the actual number of people impacted by this outbreak is likely higher and may not be limited to the states with known illnesses.

What's more, it's been difficult for investigators to determine where the outbreak originated, but they speculate a contaminated food likely introduced the outbreak strain of listeria into delis in multiple states. Investigators are still working to identify any specific products or delis that may be compromised.

To do so, they are using a system to identify illnesses that may be part of this outbreak. This system consists of a national database of "DNA fingerprints of bacteria" that cause foodborne illnesses. To date, they have discovered that the bacteria from sick people’s samples appear to be closely related genetically, which suggests that the outbreak came from the same food. It is important to note listeria spreads easily and can live for a long time in deli display cases and on equipment.

"Listeria takes advantage of the things we normally do to prevent foodborne illness to survive," says Brian Labus, PhD, MPH, REHS, an expert in infectious diseases and an assistant professor in the department of epidemiology and biostatistics at the UNLV School of Public Health. "It isn't particularly hard to kill with cooking, but the foods that spread listeria are typically not cooked, like deli meats and soft cheeses. Listeria also thrives in a cold, salty environment, and we normally use refrigeration and salt to keep bacteria from growing."

How Listeria Can Affect Pregnant People

Listeria is the third leading cause of death from foodborne illness in the U.S. with an estimated 1,600 people getting sick from the infection each year. Pregnant people are 10 times more likely than other people to get a listeria infection—and pregnant Hispanic people are 24 times more likely than others to get sick.

"Pregnancy depresses aspects of a woman’s immune system in order to prevent the body from rejecting the fetus," says Jordan C. Knight, DO, a perinatologist and OB/GYN with maternal-fetal medicine at OhioHealth Riverside Methodist Hospital. "It’s thought that this depressed immune function leaves her vulnerable to listeria bacteria."

During this recent listeria outbreak, at least one pregnant person has gotten sick and suffered a pregnancy loss. According to the CDC, pregnant people who contract listeria usually experience only fever, fatigue, and muscle aches—if any symptoms at all. But the infection can come with dire consequences for developing babies.

"Women can be asymptomatic or have general non-specific symptoms," says Dr. Knight. "These symptoms alone may be annoying, but the potential perinatal risks include pregnancy loss, growth restriction, abruption, preterm delivery, and neonatal infection and serious complications."

When someone eats food contaminated with listeria, they may not get sick right away. A miscarriage may not occur until weeks later making it difficult to identify which food was the source.

"Most listeria illnesses are mild illnesses causing fever and diarrhea like many other foodborne diseases," says Labus. "If the organism spreads beyond the gut, it can cause problems with the nervous system like headache, stiff neck, loss of balance, convulsions or confusion. In pregnant women, we usually see a more flu-like illness, with fever, fatigue, and muscle aches."

Why Pregnancy Food Avoidances Are Important

During pregnancy, people experience immune system changes that put them and their unborn children at increased risk of foodborne illness. In fact, at least 90% of those who get listeria are pregnant people and their growing infants.

"In pregnancy, the concern is not so much for the mother as it is for the developing baby," says Labus. "Listeria infections during pregnancy—especially in the third trimester—can lead to miscarriage, stillbirth, or preterm labor."

Listeria contaminates foods that you would not usually cook like deli meats, cheeses, and sprouts. It may even be found on cantaloupe, celery, lettuce, and other produce. For this reason, it is important to avoid foods that your healthcare provider advises against as well as make sure you are using good hygiene, washing your fruits and vegetables, and heating food thoroughly.

According to Dr. Knight, pregnant people are usually advised to avoid eating the following foods:

• Hot dogs, lunch meats, cold cuts (when served chilled or at room temperature)
• Refrigerated pâté and meat spreads
• Refrigerated smoked seafood
• Raw (unpasteurized) milk
• Unpasteurized soft cheeses such as feta, queso blanco, queso fresco, Brie, queso panela
• Camembert, and blue-veined cheeses
• Unwashed raw produce such as fruits and vegetables

These foods allow for listeria bacteria to grow and survive if not preventatively removed with warm temperatures, he says.

"Fortunately, severe disease in the mother is rare, though," Dr. Knight says. "Listeriosis during pregnancy results in a fetal loss in about 20% of cases and newborn death in about 3% of cases. Therefore, if a pregnant [person] is exposed to listeria and has both a high fever and symptoms, [they] should be tested for listeriosis and, at the same time, treated with antibiotics."