It seems like it pops up in the news at least once or twice a year: a listeria outbreak. For a few days, maybe a week, we’re checking the ice cream in our freezer or the prewashed spinach in our fridge to make sure it hasn’t been recalled. The news gives us a list of contaminated foods to watch out for and warns us to be careful of listeria infection, but what is listeria, exactly? Where does listeria come from? What causes it? And how worried should we be about catching listeria?

Once associated mostly with deli meat, in recent years, listeria has been found in frozen foods like ice cream, prepackaged salads, and even fully cooked chicken. Listeria is a rare but potentially deadly foodborne illness that impacts about 1,600 people every year, according to the Centers for Disease Control and Prevention (CDC).

Read on to learn more about listeria, including its impact on pregnant moms and their unborn babies, so that you can be confident in your knowledge of this rare but serious disease.

What is listeria?

Listeria is an informal name for the bacteria that causes listeria infection, also known as listeriosis (a kind of food poisoning). Listeriosis is caused by a type of bacteria called Listeria monocytogenes. These bacteria are found in soil and water, making it very easy for plants to be contaminated with it and for animals to carry it. Because of this, listeria bacteria can infect almost all the foods we eat.

Unlike a lot of other foodborne pathogens, which prefer heat and light, Listeria monocytogenes bacteria thrive in cool, dark environments. This makes it easier for the bacteria to survive the journey from their native soil to machines and equipment in facilities that process the foods that end up on our grocery store shelves.

Even if we bring home foods contaminated with listeria, it’s possible to avoid becoming ill with it by using simple precautions such as washing fruits and vegetables, heating meats and avoiding cross-contamination. This can also help prevent listeria from being spread in restaurants.

What are the signs of listeriosis?

Listeriosis can look and feel a lot like any other type of food poisoning, but it’s important to note it can be a lot more serious if left untreated. Symptoms may start within a few days or take as long as two to three months to fully develop. Listeria infection symptoms include:

  • Fever, including chills
  • Muscle aches – you might feel as if you’ve suddenly come down with the flu or participated in a high-impact workout the day before
  • Diarrhea or upset stomach similar to what you’d experience with any other kind of bad food encounter

In rare cases, the infection can spread to the nervous system. When this happens, it’s called listeria meningitis. With this kind of listeria infection, symptoms may include:

  • Headache consistent with a dull, achy feeling more than a sharp or pounding feeling
  • Stiff neck, as if you’ve gotten whiplash
  • Confusion and disorientation
  • Loss of balance and feelings of dizziness or vertigo
  • Seizures

The length of time listeriosis symptoms last depends upon several factors. It is often the case that people can get better on their own without other interventions. For more at-risk groups, if it’s detected and treated early, antibiotics can resolve the infection within a week or two. If left untreated among high-risk populations, it can get much worse and, in rare cases, lead to serious health conditions such as miscarriages or stillbirths during pregnancy, or even death.

How do you get listeria?

Where does listeria come from? Listeria causes are usually easy to determine – contaminated food and water. The CDC works hard to identify the source of the outbreak and get the outbreak under control, but it’s rarely an easy case to solve quickly. When people, particularly those at higher risk, come in contact with listeria, they may become ill. Nearly always, this means eating or drinking something that contains the bacteria. So, when you suspect listeria, look first to your food.

Is listeria contagious?

Listeria bacteria is spread by contaminated food and water. It is not contagious from person to person, however extra caution should always be taken among those who are infected. Wash your hands as you would regularly after using the bathroom, and before and after preparing and eating food to prevent a listeria infection.

Who is at risk for listeriosis?

Yes, listeria infection can be deadly, but it’s important to remember that for most people it’s not as scary as it might seem. Like many other diseases, it’s only life threatening for select populations who are already at risk. Some of the more vulnerable groups for listeriosis include:

  • People who are pregnant: When you’re pregnant, you may not suffer a great deal from listeria, but an infection can lead to serious pregnancy complications like miscarriage.
  • People living with HIV or AIDS: This is another group whose immune system isn’t as robust as the average population, so it’s important for these individuals to reduce risk of contact with listeria.
  • People undergoing chemotherapy: Chemo takes its toll on your immune system as well, so it’s also important to reduce risk of contact with listeria if you’re undergoing chemotherapy.
  • The elderly: Senior citizens may have weakened immune systems that can make them susceptible to more severe cases of listeria.

As you may be able to tell, weakened immune systems are the common denominator in the populations that should reduce their risk of exposure to listeria. Regardless of your risk status, it’s wise to be careful when handling food – and always remember to wash your hands.

Foods at high risk for carrying listeria

Listeria is a bacteria that can be found in many types of food. Even though the sources are seemingly endless, there are a few reliable culprits that are typically the cause of listeria outbreaks here in the United States.

Dairy foods, especially raw or unpasteurized dairy, can be particularly risky for listeria. Some of the repeat offenders include:

  • Soft cheeses like feta, brie and bleu cheese
  • Raw cheese, including some goat and sheep cheeses
  • Unpasteurized (raw) milk
  • Ice cream, particularly soft serve

Meats and fish have been known to carry listeria, even fully cooked chicken. The main ones to watch out for are:

  • Hot dogs
  • Sliced deli meats
  • Meat spreads
  • Smoked seafood

Vegetables and fruits can be carriers as well. Any unwashed fruits or vegetables can be dangerous, and in recent years, alfalfa sprouts have been connected with listeria outbreaks.

Does this mean that you can never sit down to a wheel of brie again? Never again enjoy the taste of a chili dog at a sports game? Is lox lost to you forever? Can this be happening?

The good news is that you don’t necessarily need to give up the foods you love. Just be aware of the risks and talk about your concerns with your care team. If you’re immunocompromised, consider cutting back until your conditions improve or eat these items in moderation. Like most diseases, the sooner it’s caught, the better the outcomes. So be aware and be careful.

Listeria in pregnancy

A pregnant woman browses the aisles at the grocery store with her cart full of lettuce, bananas, bread, and milk.

All that said, pregnancy is one condition in which your health care team may recommend that you skip the soft cheeses and other listeria-susceptible foods entirely. Believe us, we understand how hard it is. Hearing, Eat this, don’t eat that. It can be overwhelming.

You’ve probably heard, “No soft cheeses.” And the reason behind that is: Listeria. Although the risk is low, listeria can cause big complications during pregnancy.

What happens if you get listeriosis while pregnant?

It’s generally not a big deal for your personal health if you get a listeria infection while pregnant. In fact, you may not even know you have it. But if you do get listeriosis while pregnant, it can pass from you to your baby through the placenta and possibly cause serious health complications.

The biggest listeria risk is in the first trimester, when your baby is the most vulnerable. But seemingly healthy babies born with listeriosis can still suffer serious health complications.

What are the chances of getting a listeria infection while pregnant?

Researchers don’t have a lot of hard facts on listeria and pregnancy, but the medical community does know that people are up to 10 times more likely to get listeriosis during pregnancy than people who aren’t pregnant. Unfortunately, not enough is known about listeria transmission during pregnancy. We don’t know the frequency that listeria passes to an unborn child during pregnancy, nor do we know what percentage of those unborn children have serious health outcomes.

But we do know that early intervention can reduce the risk of listeria-related complications. So if you’re pregnant, it’s a good idea to get tested if you have symptoms of listeriosis. If you’re infected, you can have your baby tested and start antibiotics right away.

How to avoid getting a listeria infection when pregnant

Because there are so many unknowns about listeria, doctors must recommend erring on the side of caution during pregnancy. If you’re pregnant, you’re advised to avoid the most common foods associated with listeria, namely:

  • Soft or unpasteurized cheeses
  • Unpasteurized milk
  • Sushi and other raw fish
  • Meat spreads and pates
  • Refrigerated smoked seafood
  • Store-made salads
  • Deli meats, unheated hot dogs

Note that there are exceptions to deli meats. If they’re heated to “steaming hot,” it’s generally safe to enjoy that sandwich. Likewise, well-grilled hot dogs are safe to eat. Just be careful with the juice from the packages.

How to test for listeria

Testing for listeria is usually done with a simple blood test. During pregnancy, ultrasounds may be used to detect symptoms of listeriosis in the baby.

Listeria treatment

Healthy people who contract listeriosis generally won’t require special treatment. Symptoms may last a few days and the disease will pass. Be sure to drink plenty of water and give your body rest to recover. Ibuprofen or other over-the-counter pain medication can be used for aches and stiffness, but nothing else should be needed.

However, if your symptoms seem to be worsening rather than improving after a few days, contact a doctor or call our nurse line for advice on next steps.

For at-risk groups, particularly pregnant women, the treatment for listeria is antibiotics. It’s essential to seek treatment as soon as possible for the best recovery outcomes.

How you can prevent listeria

Listeria can tolerate the cold, but it hates heat. And like most bacteria, it really doesn’t like soap and other disinfectants. If you practice safe food prep and regular handwashing, you’re well on your way to preventing listeria. Additional tips to help prevent listeriosis and other foodborne illnesses include:

  • Cook food thoroughly, especially meat
  • Wash fruits and vegetables
  • Keep uncooked meats separate from other ingredients
  • Use pasteurized milk and dairy
  • Wash your hands
  • Don’t reuse knives or utensils that you used for uncooked meat
  • Clean up spills right away
  • Clean your refrigerator regularly and make sure it’s kept at 40 degrees Fahrenheit or lower

Additionally, take news reports about outbreaks seriously. Make sure you throw out any products that have been recalled. Don’t take unnecessary chances and be sure to alert friends and loved ones in high-risk groups about recalls as well.

What to do if you think you have listeria

If you or someone you care for is experiencing any of the symptoms mentioned above, especially if you're pregnant, contact your doctor right away. It’s always better to be safe.

People who are at particular risk should be especially vigilant for symptoms. If you suspect you were exposed to listeria and are having symptoms, call our care line or come into urgent care. Listeriosis is easily treated with supportive care, and in some cases antibiotics, but the best health outcomes happen when it’s addressed quickly, so don’t hesitate to seek care.