No doubt you’ve all heard about the outbreak of listeria in deli meat manufactured by Boar’s Head Products. It was a good lesson for Boar’s Head, which considers itself one of the finest producers of deli meat. 

The recall includes more than 70 products—including liverwurst, ham, beef salami and bologna—made at the company’s plant in Jarratt, VA. 

Boar’s Head is so popular because the company says, “We use only the finest ingredients: whole muscle beef, pork and poultry, and spices sourced from around the globe.”

This was a real wake-up call for the Boar’s Head Quality Control Department, which should have found the bacteria before the products were released to the public. How many small delis and grocery stores—perhaps even the supermarkets we trust—had to take the products off the shelf when they received the notice?

Listeria is named in honor of Joseph Lister, the British pioneer of sterile surgery. Listerine was also named after him.

Listeria infection is a foodborne bacterial illness that can be very serious. 

Listeria is especially harmful for some people:

Older adults (aged 65 and older)

People who have weakened immune systems (have health problems or take medicines that lower the body’s ability to fight germs and sickness)

Pregnant people and newborns

If you are in any of these groups, choose safer foods to protect your health or your pregnancy. 

Listeria is most commonly caused by eating improperly processed deli meats and unpasteurized milk products.

The illness is usually mild and goes away on its own. The diarrhea can last up to five days. The elderly and people with weakened immune systems have a higher risk of getting a more severe form of listeriosis, including inflammation of the brain (encephalitis).

Mild symptoms could include fever, muscle aches, nausea, vomiting and diarrhea. If the more severe form of listeriosis develops, symptoms could include headache, stiff neck, confusion, loss of balance and convulsions.

If you are at high risk of severe illness from listeria, the Centers for Disease Control (CDC) says, “Do not eat recalled deli meats. Throw them away or contact the store about returns.” In addition, it adds, do not eat any other deli meats that are sliced there unless you heat them to 165 degrees Fahrenheit or until steaming hot. 

The CDC estimates that listeria is the third leading cause of death from foodborne illness in the United States.

Listeria can also cause an intestinal illness that is usually mild. When listeria bacteria spread beyond the intestines, we call the infection invasive. The CDC only tracks listeria illnesses that are invasive.

Invasive illness in pregnant people is usually mild. However, invasive listeriosis during pregnancy usually leads to miscarriage, stillbirth, premature delivery or life-threatening infection of the newborn. Infection during pregnancy results in fetal loss in about 20 percent of cases and newborn death in about 3 percent of cases.

Other people with invasive illnesses—most commonly found in adults aged 65 years and older and people with weakened immune systems—usually have infection of the bloodstream (sepsis) or brain (meningitis or encephalitis). 

Listeria can sometimes infect other parts of the body. Among invasive illnesses not associated with pregnancy, most people need to be hospitalized (about 87 percent of cases) and about one in six people die.

What should I do if I ate food that may have been contaminated with listeria?

Contact a health care provider if both of the following things apply to you:

You ate food that has been recalled or linked to an outbreak.

You have a fever and other symptoms of listeriosis, such as fatigue and muscle aches.

Let the health care provider know if you ate possibly contaminated food. This is especially important if you are pregnant, aged 65 or older or have a weakened immune system.

If you eat food possibly contaminated with listeria and do not feel sick, most experts believe you do not need tests or treatment. Talk with a health care provider if you have questions about what to do.

Opened packaged deli meats should NOT be kept in the refrigerator longer than three to five days. If you are hungry, go to the fridge, find a package of opened deli meat and don’t know how long it’s been there, don’t even think about it. Throw it out. 

It’s good to have a permanent marker near the fridge to date some of the products you put into it.

Michael Kossove is Professor Emeritus and adjunct professor of microbiology at Touro University, School of Health Sciences.