What to know about listeria and the foodborne illness it causes

Helmut Albrecht, MD

Internal Medicine

From time to time, we hear about listeria outbreaks that have caused serious illness or sometimes even death, resulting in widespread recalls of everything from cantaloupe to deli meat. News like this can be scary and leave us wondering how concerned we need to be about listeria.

Infectious disease expert Helmut Albrecht, MD, explained what to know about listeria including who’s most at risk from infection and how to prevent disease.

What is listeria?

Listeria is a type of bacteria found in contaminated food that can cause the foodborne illness listeriosis. Unlike most foodborne illnesses, however, listeria bacterium is resistant to refrigeration.

“It’s not killed by cold temperatures, so it can live in your fridge and survive on surfaces in your kitchen for a quite a while,” Dr. Albrecht explained.

This means food infected with listeria can spread and contaminate other surfaces and foods. Most people with a healthy immune system can fight off a listeria infection pretty easily, but listeriosis can be dangerous for certain groups.

Who is most at risk for a listeria infection and what are the symptoms?

Groups most at risk for listeriosis are older adults who are over 65, pregnant women, very young infants and people with compromised immune systems, such as those with cancer, diabetes and HIV/AIDS.

“The infection typically starts with a mild gastrointestinal illness,” Dr. Albrecht said, “but people who are at higher risk may not be able to contain the infection and so it spreads throughout the body. If it reaches the bloodstream, you’ll usually see flu-like symptoms such as fever, muscle aches and fatigue.”

Then, from the bloodstream, there are two organ systems listeria targets. One is the brain, causing the life-threatening illness called meningitis. Symptoms of meningitis include headache, stiff neck, confusion, loss of balance and seizures.

The other organ listeria targets is the placenta in pregnant women.

“There is a very serious threat of losing the pregnancy or having premature birth because of listeria’s affinity to the placenta,” he said. “Women who are pregnant can also get a flu-like illness, and they can have a meningitis, but they’re at significantly higher risk of premature birth or losing the pregnancy.”

What should you do if you think you have consumed food contaminated with listeria?

If you think you might have consumed a product that has been recalled, Dr. Albrecht said to keep an eye out for any symptoms. If you are in a group that’s more at risk for serious infection and you develop symptoms, call your doctor.

“You also want to clean surfaces that product may have touched,” Dr. Albrecht said. “The incubation period can be short as a day but can be as long as ten days.”

How is listeriosis treated?

“Several standard antibiotics, essentially regular penicillin, treat this in the vast majority of cases,” Dr. Albrecht said. “It is not difficult to treat.”

The biggest challenge is in diagnosing it early because a listeria infection often looks like influenza or other gastrointestinal illnesses. Once a listeria infection reaches the brain, it is a serious illness that can have long term aftereffects caused by the disease.

“If it is discovered late (i.e., at the meningitis stage), and especially if the patient has an immune system issue, patients may experience significant aftereffects or ongoing issues,” Dr. Albrecht said. “However, most people are treated successfully. It’s important to do the right tests and get therapy on board as quickly as possible.”

How can listeria infection be prevented?

Most people can protect themselves from listeria by properly washing and handling food and by being aware of product recalls.

If you fall into a high-risk group, the Centers for Disease Control and Prevention

recommends going the extra step of avoiding certain foods that are more at risk for listeria contamination, such as:

• Unpasteurized dairy products
• Unheated deli meat
• Premade salads
• Refrigerated meat spreads
• Smoked fish
• Raw or lightly cooked sprouts
• Cut melon left out for more than 2 hours (1 hour if temperatures are above 90 degrees Fahrenheit)