Mushrooms, soft cheeses, frozen waffles, precooked chicken, deli meats …

Over the past several months, there have been many headline-grabbing recalls of foods sold around the country. Many of those recalls have centered around products potentially contaminated with Listeria. The headlines can be unnerving, and many people aren’t sure what steps to take if they purchased or ate food at risk of Listeria contamination. In this editorial, we break down what Listeria is, the risks it poses to healthy adults and at-risk groups, and how to respond to product recalls.

1. What’s the difference between Listeria and listeriosis?

Listeriosis is the infection caused by the gram-positive bacteria Listeria monocytogenes, usually when contaminated food is eaten. We tend to think of refrigerated food as safe to eat, but that’s not always the case. Listeria bacteria can grow in food at refrigerator temperatures, and it can survive in the freezer. That makes refrigerated, packaged, ready-to-eat products (that require no cooking before they are eaten) particularly at risk for contamination. Sprouts, melons, and other fruits and vegetables can also pose a risk.

2. What are the risks of listeriosis?

Most of the time, individuals with healthy immune systems do not have to worry too much about Listeria exposure. However, listeriosis is one of the most fatal foodborne illnesses for individuals with weakened immune systems. People with listeriosis typically have chills, fever, and muscle aches (resembling the flu), with nausea, vomiting, and diarrhea. Usually, symptoms resolve in 1 to 7 days.

The bacteria sometimes enter the bloodstream from the intestine and invade certain organs. This is known as invasive listeriosis. Invasive listeriosis can spread to the tissues covering the brain and spinal cord (causing meningitis), the eyes, heart valves (causing endocarditis), and joints. In pregnant women, it can spread to the uterus and fetus. In the United States, invasive listeriosis develops in only about 1,600 people each year, and about 260 people die of it.

3. Who’s at risk?

Listeriosis is most common among the following groups:

• Pregnant women
• Fetuses and newborns
• People aged 60 or older
• People with a weakened immune system, such as those with human immunodeficiency (HIV) infection
• Individuals on immunosuppressant medications

Pregnant women are about 10 times more likely to get listeriosis than the general population, and pregnant Hispanic women are about 24 times more likely to get listeriosis than the general population. Listeriosis is the reason most doctors recommend pregnant women avoid deli meats and other foods that could be contaminated. As the percentage of Americans over the age of 65 grows, older individuals need to be aware of the risks and warning signs of listeriosis and take necessary precautions. 

4. Why do there seem to be so many recalls of Listeria recently?

With all the recent headlines, it’s easy to assume listeriosis is on the rise nationwide. The reality is, there are several factors that impact the number of recalls and related media coverage.

For starters, we have strong food safety protocols in America. Listeria contamination may not necessarily be significantly on the rise, but we are more attuned to looking for it. At the same time, an increase in consumption of processed and prepared foods, where Listeria is more likely to be present, are likely contributing factors.

People should also know that an “outbreak” can be less threatening than they may think. We tend to think of an outbreak as dozens or hundreds of people. But the definition of a foodborne illness outbreak is just two or more people getting sick from eating the same contaminated food or drink. Tracking outbreaks can be challenging as it can take up to 10 weeks for a person to get sick after exposure to Listeria, and many healthy individuals will never get sick or show symptoms. That makes tracing illnesses back to individual exposures difficult.

5. What should I do if I purchased or ate a product contaminated with listeria?

It’s a good idea to pay attention to recalls, especially for individuals who may be at greater risk. If you purchased a product that could be contaminated, the first step is to dispose of it. You should also thoroughly clean the refrigerator and other potential areas of cross contamination.

In most cases, cooking the food will kill the Listeria bacteria. But if you or a family member ate the product uncooked, it’s important to monitor for symptoms and be prepared to seek medical attention immediately.