How common is listeria?

This sheet talks about exposure to listeriosis in pregnancy and while breastfeeding. This information should not take the place of medical care and advice from your healthcare provider.

What is listeriosis?

Listeriosis is an infection caused by Listeria monocytogenes bacteria, often called just Listeria. Listeriosis is typically caused by eating food that has been contaminated with Listeria. Listeria can be found in your home, in restaurants and other places such as the grocery store or food processing plants. Food with listeria can introduce the infection into the refrigerator which can spread to other foods. Listeria can continue to live in cold temperatures, such as in the refrigerator, but the chance for spreading can be slowed if the refrigerator is kept at a temperature of 40 degrees Fahrenheit or lower.

Some of the foods that are more likely to be contaminated with Listeria include unpasteurized (raw) milk, uncooked meat and fish, uncooked vegetables, lunch meat and soft cheeses. However, the largest recent outbreak occurred in cantaloupes.

Who is at risk for listeriosis?

The people most vulnerable to listeriosis include: pregnant women, young children, adults over the age of 60, and people with weakened immune systems. Following some simple food safety guidelines can reduce the chance of listeriosis.

What precautions should I take to avoid the infection?

To decrease the risk of listeriosis and other food-borne illness in all individuals:

  • Do not drink unpasteurized milk (also called raw milk) or eat any foods made with unpasteurized milk.
  • Thoroughly cook raw foods from animal sources.
  • Heat foods to at least 165°F (to steaming), to kill the bacterium.
  • Wash raw vegetables and fruit, even if you plan to peel them (to remove skin).
  • Separate uncooked meats from cooked meats and vegetables.
  • Wash your hands, cutting boards, knives, counters, and sinks after contact with uncooked foods.
  • Consume ready-to-eat foods as soon as possible.
  • Keep your refrigerator at or below 40 degrees Fahrenheit (4 degrees Celsius).
  • Clean your refrigerator regularly.

Pregnant women should take additional precautions to decrease the risk of listeriosis:

  • Do not eat soft cheeses (such as feta, Brie, Camembert, blue-veined cheeses and Mexican-style cheeses such as queso blanco, queso fresco and Panela) unless they have labels stating that they are made from pasteurized milk. However, it should be noted that some Mexican style cheeses made from pasteurized milk have been a source of Listeria infections possibly due to the cheese making process.
  • Reheat, to at least 165°F / to steaming, any leftovers, ready-to-eat foods, hot dogs, cold cuts, deli meat, frozen vegetables and frozen prepared foods.
  • Take care to not get the juice of deli meats and hot dogs on other foods/surfaces and wash your hands after handling deli meats and hot dogs.
  • Do not eat pâté, meat spreads or refrigerated smoked seafood, unless it is an ingredient in a fully cooked dish (like a casserole).
  • Avoid ready to eat salads.

How do I know if I’ve been infected with Listeria?

Not everyone affected with Listeria will develop symptoms. Symptoms of listeriosis range from showing no symptoms to having diarrhea, fever, muscle pain, joint pain, headache, stiff neck, backache, chills, sensitivity to bright light, and/or sore throat with fever and swollen glands. These symptoms can begin days to weeks after eating contaminated food. A blood test can confirm whether you have been infected with listeriosis. If you have eaten contaminated food and do not have symptoms, some experts feel no special testing or treatment is needed. Be sure to discuss this with your health care provider.

I am pregnant and have been infected with Listeria. Will this affect my pregnancy or the baby?

Listeria infection during pregnancy can cause miscarriage, stillbirth, uterine infection and preterm delivery. Listeriosis has not been linked to a pattern of birth defects.

Listeriosis during pregnancy can also increase the chance for serious health problems for the newborn. Newborn babies infected with Listeria can develop either early onset or late onset listeriosis. Early onset listeriosis develops 1-2 days after birth, and the baby often has signs of a serious bacterial infection. Late onset listeriosis occurs 1-2 weeks after birth, and usually includes symptoms of meningitis. Late onset listeriosis is most likely related to Listeria present in the mother’s birth canal.

Not all babies whose mothers are infected during pregnancy will have problems due to listeriosis. Early diagnosis and treatment with high doses of antibiotics might prevent infection of the unborn.

Are there any treatments for listeriosis during pregnancy?

Yes, large doses of antibiotics have been recommended. Therapy for maternal listeriosis with high doses of antibiotics has resulted in successful therapy, leading to lower incidences of premature deliveries and stillbirths. Your healthcare providers will talk with you about the right treatment for your pregnancy.

Is there any way to know if the baby has been infected or harmed by listeriosis?

An ultrasound to look at the baby can be used to check for an enlarged heart, thickened bowel, and increased thickness of the stomach walls, which may occur in some babies infected with Listeria. A blood test can be performed on the baby after birth to detect whether the baby has been infected with Listeria.

Can Listeria be passed to the baby through breast milk?

It is unknown if listeria can be transmitted through breastmilk. If you have been diagnosed with listeria and are breastfeeding, talk to your healthcare provider.

Does it matter if the baby’s father was exposed to Listeria before I got pregnant?

There is no evidence linking paternal exposure to Listeria with a higher chance of infection during pregnancy. In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/pdf/.

Please click here for references.

Listeria Fact Sheet

This page contains information on Listeria.

Page last updated: 24 July 2019

What is Listeriosis

Listeriosis, is a rare but serious disease caused by the bacteria Listeria monocytogenes (L. monocytogenes) that can survive and grow on certain high risk foods. While it is probably common for people to eat foods contaminated with a small amount of the bacteria, only some people are at risk of becoming sick. The people who do get sick may require hospitalisation and it may lead to death.

What are the symptoms?

Listeriosis can cause different symptoms depending on which part of the body has been affected and the usual health of the person. Symptoms can include fever, muscle aches, and sometimes nausea and diarrhoea. Infection with L. monocytogenes may also cause septicaemia (blood poisoning) and meningitis (inflammation of the outside of the brain), and death can occur because of these complications.

Pregnant women generally experience mild symptoms themselves; however infections during the pregnancy can lead to miscarriage, stillbirth or infection of the newborn baby.

Symptoms usually start between 3 to 70 days (average 21 days) after eating food contaminated with the bacteria.

How is it spread?

L. monocytogenes is commonly found in the environment (such as soil) and some raw foods. Unlike many other bacteria, L. monocytogenes are unusual because they can grow in the refrigerator. Eating foods that contain L. monocytogenes does not cause illness in most people however some can become sick. Babies can be born with listeriosis if their mothers eat contaminated food during the pregnancy.

Listeriosis does not spread from person-to-person.

Who is at risk?

Eating foods that contain L. monocytogenes does not cause illness in most people. The disease mainly affects the elderly, pregnant women and their unborn and newborn babies, and people with weakened immune systems due to illness or medication (for example, people on cancer treatment or steroids, and people with diabetes, kidney disease, liver disease and HIV infection).

How is it prevented?

If you (or someone in your household) have a weakened immune system or are pregnant, the best way to avoid L. monocytogenes is to eat freshly cooked or freshly prepared food.

Try to avoid foods that have a higher risk of L. monocytogenes contamination such as:

  • chilled seafood such as raw oysters, sashimi and sushi, smoked ready-to-eat seafood and cooked ready-to-eat prawns
  • cold meats from delicatessen counters and sandwich bars, and packaged, sliced ready-to-eat meats
  • cold cooked ready-to-eat chicken (whole, portions, or diced)
  • rockmelon
  • pre-prepared or pre-packaged fruit or vegetable salads, including those from buffets and salad bars
  • soft, semi-soft and surface-ripened cheeses such as brie, camembert, ricotta, blue and feta
  • refrigerated paté or meat spreads
  • soft serve ice cream
  • unpasteurised dairy products.

You can further reduce your risk by:

  • avoiding food that is past its best before or use by date
  • refrigerating leftovers promptly and using them within 24 hours, or freezing them
  • cooking food thoroughly
  • reheating food until it is steaming hot.

The NSW Food Authority provides further information on foods to eat and avoid during pregnancy.

How is it diagnosed?

The diagnosis of listeriosis can be confirmed by blood or other tests requested by a doctor.

How is it treated?

Treatment for listeriosis involves antibiotics and supportive care. When infection occurs during pregnancy, antibiotics can often prevent infection of the unborn baby or newborn.

Listeria in Australia

While listeriosis can be a very severe illness, the number of cases reported in Australia each year is relatively low, with around 80 cases reported each year. Most people infected with listeriosis are not connected to an outbreak, however outbreaks can occur. Outbreaks caused by listeriosis have been associated with rockmelon, delicatessen meats, raw milk, soft cheeses, pre-prepared salads (for example, from salad bars), unwashed raw vegetables, paté, cold diced chicken and pre-cut fruit and fruit salad.

Preventing the spread of listeria in Australia

Listeriosis is mainly acquired by eating contaminated foods. Food safety standards in Australia are designed to minimise the contamination of food with bacteria including L. monocytogenes. It is difficult to completely remove the risk as this bacteria is so widespread in the environment. Cases of listeriosis are reported to public health authorities so outbreaks can be identified and managed, and particular causes detected.

Further Information

Talk to your doctor about preventing listeriosis if you are pregnant or if you think you might be at increased risk due to illness or medications.

More information on listeriosis can also be found by contacting your state or territory health department.

In this section

  • Dengue Fact Sheet
  • Listeria Fact Sheet
  • Tick bite prevention

Pregnant women are constantly warned about the dangers of listeria.

Listeria is a type of food-borne bacteria that can be in a number of everyday foods. It can also be found in soil, animal faeces, vegetation and sewage. The possibility is very high of listeria entering and contaminating our food supply. This is why we all need to be very careful.

The levels commonly found in foods are generally harmless to the average person with a healthy immune system. However, during pregnancy if you eat listeria contaminated food and contract an infection you and your baby could be at risk.

Women who are pregnant are at a higher risk than the rest of the population of becoming infected. . This is because of changes to their metabolism and immunity, making them more susceptible.

The problem with listeria in pregnancy

Listeria can cause a rare but dangerous infection called listeriosis. If you contract listeriosis while pregnant the bacteria could reach your baby via the placenta. If this happens, there is a risk of a number of complications. These include blood poisoning, miscarriage, and premature labour or even stillbirth.

One difficulty with listeriosis is that it can easily be misdiagnosed. This is because the symptoms are easy to confuse with having influenza or another viral illness. Common, shared symptoms include; a fever or chills, muscle aches and back pain, diarrhoea and nausea.

The good news is that listeriosis in pregnant women is very rare in Australia and New Zealand. If you avoid soils and foods at risk of being contaminated it’s very unlikely that you will be infected. It is also important to follow safe hygiene habits when preparing and cooking foods.

Treatment for listeriosis

If you think you might have come into contact with listeria while you are pregnant and are feeling unwell, tell your healthcare professional. A blood or amniotic fluid test can confirm whether you have contracted listeriosis.

If your results are positive, a course of antibiotics will help to fight the infection. If diagnosed early enough, antibiotic treatment can also prevent the infection from being passed to your baby.

Avoiding listeria in pregnancy

Practising good food hygiene is the best way to avoid coming into contact with listeria.

Practise these simple steps whenever you are preparing or choosing food to eat:

  • Always wash your hands
  • Thoroughly wash fresh fruit and vegetables
  • Cook all food, especially meat, seafood and dairy products, all the way through to kill the bacteria
  • Serve and eat your meals while they are hot
  • Reheat left overs or ready to eat foods until they are steaming hot
  • Store any leftovers in the fridge immediately and eat within 12 hours of cooking
  • Avoid all raw or partially cooked meats, seafood and soft cheeses
  • Wash all cooking utensils and chopping boards with hot soapy water
  • Avoid eating any food you’re not sure about

Certain foods are at higher risk of contamination with listeria. To be on the safe side, avoid these foods during pregnancy:

  • Soft white and blue cheeses
  • Soft-serve ice cream
  • Any dairy products made from un-pasteurised milk
  • Deli meats
  • Pâté
  • Pre-made and refrigerated salads, including fruit salads
  • Seed sprouts
  • Raw or smoked seafood including sashimi and oysters
  • Cooked and chilled seafood including prawns
  • Smoked salmon or trout
  • Sushi

While You’re Pregnant Main Page

What Is Foodborne Illness? | Listeria | Toxoplasma

Spanish (Español)

Listeria: Frequently Asked Questions

“What is Listeria monocytogenes?”

It’s a harmful bacterium that can be found in refrigerated, ready-to-eat foods (meat, poultry, seafood, and dairy – unpasteurized milk and milk products or foods made with unpasteurized milk), and produce harvested from soil contaminated with L. monocytogenes. Many animals can carry this bacterium without appearing ill, and thus, it can be found in foods made from animals. L. monocytogenes is unusual because it can grow at refrigerator temperatures where most other foodborne bacteria do not. When eaten, it may cause listeriosis, an illness to which pregnant women and their unborn children are very susceptible.

“How could I get listeriosis?”

By eating ready-to-eat meats, poultry, seafood, and dairy products that are contaminated with L. monocytogenes. You can also get listeriosis by eating contaminated foods processed or packaged in unsanitary conditions or by eating fruits and vegetables that are contaminated from the soil or from manure used as fertilizer.

“How could listeriosis affect me?”

The symptoms can take a few days or even weeks to appear and may include fever, chills, muscle aches, diarrhea or upset stomach, headache, stiff neck, confusion, and loss of balance. In more serious cases, listeriosis could also lead to the mother’s death.
Most of the time, pregnant women who are infected with listeriosis don’t feel sick. However, they can pass the infection to their unborn babies without even knowing it. That’s why prevention of listeriosis is very important. In any case, if you experience any of the above symptoms, see your doctor or healthcare provider immediately.

Facts

  • Pregnant women are about 10 times more likely to get listeriosis than other healthy adults.
  • An estimated 1/6 of all Listeria cases occur in pregnant women.

(Centers for Disease Control and Prevention)

“How could listeriosis affect my baby?”

During the first trimester of pregnancy, listeriosis may cause miscarriage. As the pregnancy progresses to third trimester, the mother is more at risk. Listeriosis can also lead to premature labor, the delivery of a low-birth-weight infant, or infant death. Fetuses who have a late infection may develop a wide range of health problems, including intellectual disability, paralysis, seizures, blindness, or impairments of the brain, heart, or kidney. In newborns, L. monocytogenes can cause blood infections and meningitis.

Listeriosis & Pregnant Hispanic Women

Studies show that pregnant Hispanic women may have a higher incidence of listeriosis than pregnant non-Hispanic women. This is most likely because they might make and eat homemade soft cheese and other traditional foods made from unpasteurized milk. “Queso fresco”- a traditional homemade cheese, prepared from unpasteurized milk and widely consumed by Hispanics – has led to miscarriages, death of newborns, and premature delivery caused by L. monocytogenes.
To prevent the risk of listeriosis, Hispanic pregnant women should not eat homemade soft cheeses and other traditional foods made from unpasteurized milk. Like all other pregnant women, they should follow the food safety precautions outlined below.

“How can I prevent listeriosis?”

The good news is that listeriosis can be prevented! Here’s how…

Time to Chill

  • Your refrigerator should register at 40° F (4° C) or below and the freezer at 0° F (-18° C). Place a refrigerator thermometer in the refrigerator, and check the temperature periodically. During the automatic defrost cycle, the temperature may temporarily register slightly higher than 40° F. This is okay.
  • Refrigerate or freeze perishables, prepared food, and leftovers within two hours of eating or preparation. Follow the 2-Hour Rule: Discard food that’s left out at room temperature for longer than 2 hours. When temperatures are above 90° F (32° C), discard food after 1 hour.
  • Use ready-to-eat, perishable foods, such as dairy, meat, poultry, seafood, and produce, as soon as possible.

Fridge TIPS

  • Clean your refrigerator regularly.

  • Wipe up spills immediately.

  • Clean the inside walls and shelves with hot water and a mild liquid dishwashing detergent; then rinse.

  • Once a week, check expiration and “use by” dates, and throw out foods if the date has passed. Follow the recommended storage times for foods.

Refrigerator & Freezer Storage Chart (PDF).

To Eat or Not to Eat?

Don’t eat:

  • Hot dogs, deli meats, and luncheon meats – unless they’re reheated until steaming hot.

  • Soft cheeses like Feta, Brie, and Camembert, “blue-veined cheeses,” or “queso blanco,” “queso fresco,” or Panela – unless they’re made with pasteurized milk. Make sure the label says, “made with pasteurized milk.”

  • Refrigerated pâtés or meat spreads.

  • Refrigerated smoked seafood – unless it’s in a cooked dish, such as a casserole. (Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna, or mackerel is most often labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky.” These types of fish are found in the refrigerator section or sold at deli counters of grocery stores and delicatessens.)

  • Raw (unpasteurized) milk or foods that contain unpasteurized milk.

It’s okay to eat:

  • Canned or shelf-stable (able to be stored unrefrigerated on the shelf) pâtés and meat spreads.
  • Canned or shelf-stable smoked seafood.
  • Pasteurized milk or foods that contain pasteurized milk.

Note: See your doctor or healthcare provider if you have questions about listeriosis.

What All Pregnant Women Should Know About Listeria and Listeriosis

Usually the most serious risks associated with a Listeria infection in someone who is pregnant are those posed to the unborn child. iStock

Most healthy people have little to fear from listeria. The bacteria can cause mild flu-like symptoms in healthy adults, but its more serious repercussions — including death and systemic infection — nearly always strike seniors and those with a weakened immune system. But getting infected with listeria during pregnancy is a major exception to that rule.

Pregnant women and their newborns are more likely to get a listeria infection, which is called listeriosis, than other healthy individuals, according to the Centers for Disease Control and Prevention (CDC). (1) And Hispanic women who are pregnant are at an even greater risk: they are 24 times more likely to be diagnosed with a listeria infection compared with other health adults. (1)

Why are pregnant women so much more likely to develop listeriosis? Pregnancy depresses aspects of a woman’s immune system in order to prevent her body from rejecting the fetus. (2) It’s thought that this depressed immune function leaves her particularly vulnerable to harmful listeria bacteria. (3)

RELATED: Why Listeria Makes You Sick

Certain types of soft cheeses — including ones used in “Hispanic-style” cooking, such as queso fresco and queso blanco — are more likely than most other foods to be made with unpasteurized milk, and therefore may harbor harmful listeria bacteria. (4) Hispanic women may be at higher risk of listeriosis because their traditional dietary habits may be more likely to include these “raw” cheeses, according to the U.S. Food and Drug Administration (FDA). (5)

RELATED: How to Prevent Listeria Infection

It’s important to point out that the more severe risk of listeriosis when it comes to pregnant women is for the unborn child rather than the mother.

“Severe disease in the mother is rare,” says Jennifer Hunter, DrPH, an epidemiologist with the CDC, who is based in Atlanta. While some women experience no symptoms at all, Hunter says that listeria in pregnancy usually causes the same mild flu-like side effects that it causes in healthy adults. The symptoms of listeria in pregnancy include diarrhea or stomachache, which may be followed by fever, headaches, and body aches. (6)

Because all of these symptoms of listeriosis are common ones, and not specific to the infection, the odds are good that they’re caused by something other than listeria infection. (6) But it’s still a good idea to report symptoms to your doctor to monitor the fetus for signs it may be infected.

Listeria Exposure During Pregnancy

At your first prenatal visit, your health care provider likely talked with you about all the foods you should avoid during pregnancy — sushi, raw meat, deli meat and unpasteurized cheese — to prevent exposure to listeria. That’s because consuming this bacteria can sometimes make you sick, and that extremely unlikely possibility becomes more likely when you’re expecting. Fortunately, there are steps you can take to greatly reduce your risk. Here’s how, along with what happens if you think you’ve been exposed.

What is listeriosis?

Listeriosis is an illness caused by eating foods contaminated with the listeria monocytogenes bacteria. Keep in mind that simply being exposed to listeria, however, doesn’t mean you’ll develop an infection. In fact, most women who are exposed to listeria will not develop a listeriosis infection.

The risk of listeriosis during pregnancy

While the odds of being infected with listeriosis is still very, very low, it is significantly (13 times) higher during pregnancy — and the potential of its causing problems in pregnancy is higher. Listeria, unlike many other germs, enters the bloodstream directly and therefore can get to the baby quickly through the placenta (other food contaminants generally stay in the digestive tract). And an untreated infection can put baby at increased risk of more serious complications, including miscarriage, preterm labor, stillbirth or meningitis in newborns.

Symptoms of listeriosis

Listeriosis can be hard to detect, partly because symptoms can develop up to two months after eating contaminated food and can vary from severe to mild. If you think you may have eaten food that contains listeria, watch for flu-like symptoms including:

  • Fever over 100.6°F
  • Muscle pain
  • Backache
  • Headache
  • Gastrointestinal symptoms, including diarrhea

Note that you may have fever only, or you might not have any symptoms at all. So it’s important to contact your doctor even if you think what you’re experiencing might be caused by something else.

Read More about What to Eat and Avoid During Pregnancy

Your Health Foods to Avoid During Pregnancy Your Health 11 Best Foods to Eat While Pregnant Your Health Foods to Avoid During Pregnancy Your Health 11 Best Foods to Eat While Pregnant

If you think you’ve been exposed to listeria

In many cases, a watch-and-wait approach for symptoms is all that’s necessary.

If you’re experiencing symptoms and your doctor suspects a listeriosis infection, he may order blood or other various tests to check for the bacteria and monitor your baby’s health. If you have been infected, you’ll get a prescription for antibiotics.

What should you do to protect yourself

One of the best ways to prevent listeriosis is to avoid foods that are most likely to be contaminated. These include:

  • Hot dogs, lunch meats or cold cuts that are cold or heated lower than 165 degrees
  • Refrigerated pâté and meat spreads
  • Refrigerated, smoked seafood (like smoked salmon)
  • Unpasteurized milk and soft cheeses (like feta, queso blanco, Brie and blue-veined cheeses)
  • Unpasteurized fresh fruit juice and veggie juice (if you’re not sure whether a juice has been pasteurized, don’t drink it)
  • Unwashed, raw produce
  • Alfalfa and other sprouts

A few more tips to stay safe:

  • Always wash produce (including those organic blueberries from the farmer’s market) thoroughly in running tap water, even if you’re planning to peel or cook it.
  • As a precaution, even ready-cooked meats should be heated to steaming before eating.
  • When eating out, watch for signs that the restaurant doesn’t follow basic sanitation rules (and it should be pretty obvious): Perishable foods are kept at room temperature, the bathrooms are unclean, it’s open season for flies, etc.

Unfortunately it’s impossible to know for sure if the food you buy today will be recalled tomorrow — making it impossible to avoid listeria entirely. That said, the risk of contracting the infection from day-to-day eating is extremely low, even if you are expecting. So try not to let worries about possible food contamination consume you. Instead, spend your energy focusing on what you can do: Eat a balanced, healthy pregnancy diet to help support you and your growing baby.

Listeria infection – including symptoms, treatment and prevention

Food recalls for Drakes Premium Gourmet Selection silverside listeria and Washed Rind Cheese Listeria

Bacterial infection caused by Listeria monocytogenes is called listeriosis.

Listeria infection is a notifiable condition1

How Listeria is spread

These bacteria are widespread in nature, being found in soil, decaying vegetation and the bowels of many mammals.

Listeria infection is mainly spread by eating contaminated foods. Unlike most bacteria, Listeria can multiply in refrigerated foods, if they have been contaminated. Contact with infected farm animals, particularly stillborn animals, can also spread the infection.

Foods at higher risk

Foods associated with the spread of Listeria include:

  • unpackaged ready-to-eat cold meats and packaged sliced ready-to-eat cold meats. For example from delicatessen counters, sandwich bars or supermarkets
  • cold cooked ready-to-eat chicken purchased whole, in portions or diced
  • refrigerated pâté or meat spreads
  • pre-prepared or pre-packaged fruit or vegetable salads, for example salad bars or smorgasbords
  • chilled seafood, including:
    • raw seafood, for example oysters, sashimi or sushi
    • smoked ready-to-eat seafood
    • cooked peeled prawns, for example prawn cocktails, sandwich fillings and prawn salads
  • soft, semi-soft and surface ripened cheeses, either pre-packaged or from the delicatessen. For example, brie, camembert, ricotta, feta and blue
  • soft serve ice cream
  • other unpasteurised dairy products (for example raw goat’s milk).

Signs and symptoms

People are probably frequently exposed to Listeria, with only mild illness resulting. However, infection is more serious when it occurs in newborn babies, the elderly, immune suppressed people and pregnant women.

Symptoms may include:

  • sudden onset of fever
  • headache
  • backache
  • nausea, vomiting
  • neck stiffness
  • gradual onset of confusion, decreased alertness.

Pregnant women may have relatively mild symptoms (fever and aches) and make a quick recovery. However, they may transfer the infection to their unborn child who may be stillborn or born very ill.

Diagnosis

The diagnosis is made by growing the bacteria from a sample of cerebrospinal fluid (cerebrospinal fluid: the fluid surrounding the brain and spinal cord), blood or from samples taken from the baby.

Incubation period

(time between becoming infected and developing symptoms)

Varies from 3 to 70 days. The average is 3 weeks.

Infectious period

(time during which an infected person can infect others)

Except for transmission from a pregnant woman to her fetus, person-to-person spread does not occur.

Treatment

Antibiotic treatment and hospital admission may be required.

Prevention

Exclusion from childcare, preschool, school and work is not necessary.

Pregnant women and immune suppressed people

Pregnant women and immune suppressed people should take special care to avoid foods which may be contaminated with Listeria. They should follow these guidelines:

  • eat freshly cooked or freshly prepared foods
  • eat well washed, freshly prepared fruit and vegetables
  • cook foods thoroughly, especially meats
  • reheat foods to ‘steaming’ hot
  • make safer food choices and avoid higher risk foods
  • avoid ready-to-eat food from salad bars, sandwich bars, delicatessens and smorgasbords
  • avoid foods that are past their ‘best before’ or ‘use by’ date
  • only buy ready-to-eat hot food if it is steaming hot
  • if eating out, order hot meals
  • after handling uncooked food, wash hands, knives and cutting boards with detergent and hot water
  • avoid the use of untreated manure on vegetable crops which will be eaten raw
  • avoid contact with sick or stillborn farm animals.

Useful links

  • Preventing food poisoning at home
  • Pasteurised milk v’s unpasteurised milk
  • When you have a notifiable condition
  • Food Standards Australia and New Zealand
  • Food Safety Information Council Listeria quiz
  • Food Safety Information Council Listeria fact sheet

1 – In South Australia the law requires doctors and laboratories to report some infections or diseases to SA Health. These infections or diseases are commonly referred to as ‘notifiable conditions’.

Symptoms

Listeriosis can cause a variety of symptoms, depending on the person and the part of the body affected. Listeria can cause fever and diarrhea similar to other foodborne germs, but this type of Listeria infection is rarely diagnosed. Symptoms in people with invasive listeriosis, meaning the bacteria has spread beyond the gut, depend on whether the person is pregnant.

  • Pregnant women: Pregnant women typically experience only fever and other flu-like symptoms, such as fatigue and muscle aches. However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.
  • People other than pregnant women: Symptoms can include headache, stiff neck, confusion, loss of balance, and convulsions in addition to fever and muscle aches.

People with invasive listeriosis usually report symptoms starting 1 to 4 weeks after eating food contaminated with Listeria; some people have reported symptoms starting as late as 70 days after exposure or as early as the same day of exposure.

Learn more >

How Common Is Listeria During Pregnancy? An OB-GYN Explains The Risk

When you first get pregnant, at least for me, in addition to everyone asking me what I was having, I got a ton of unsolicited advice about what I was allowed to eat. “No raw eggs, deli meat, or soft cheese now,” everyone would smugly remind me. “You don’t want to get listeria.” But just how common is listeria during pregnancy? Is it OK to splurge and have a little taste of that unpasteurized brie? What are the chances that I’ll actually contract listeria?

Thankfully, listeria isn’t that common during pregnancy, according to Dr. Jamil Abdur-Rahman, an OB-GYN and medical travel blogger along with his twin brother for TwinDoctorsTV. He says in an email interview with Romper that according to the Centers for Disease Control and Prevention (CDC), there are only 1600 cases of listeria documented in the U.S. annually. “Of these 1600 cases, roughly one in every seven of them are seen in pregnant women. This means that we see about 200 to 300 cases of listeria in pregnant women annually. While this number isn’t that impressive on its face, consider the fact that one in seven (i.e., 14 percent) of Americans are not pregnant,” he explains. “So if only two percent of Americans are pregnant at any one time, but 14 percent of listeria infections are seen in pregnant people, then the infection is dramatically overrepresented in pregnant women.”

Giphy

Why are pregnant women more susceptible to listeria, even though it’s uncommon to contract? Abdur-Rahman says that pregnant women are seven times more likely to contract listeria because their immune systems aren’t as active as non-pregnant people’s immune systems. “The reason for this is that a growing fetus is a ‘foreign invader’ as far as a pregnant woman’s immune system is concerned. After all, that growing fetus’ genetic material is half familiar to mom’s immune system, but the other half is not. So, if a pregnant woman’s immune system were not somewhat compromised, it would attack the ‘foreign invader’ growing within its womb,” Abdur-Rahman explains. Since the immune system is “tamped down,” it’s good for your little “foreign invader,” but “bad for fighting off infection.”

Abdur-Rahman says to stay away from unpasteurized dairy products, unwashed fruits and veggies, and lunch meats in order to be less likely to contract listeria. Thankfully, in the U.S., most of our food standards and food safety laws are pretty good at preventing listeria, but it never hurts to use caution. “When food that contains listeria has been ingested, the bacteria can then enter a person’s bloodstream. Once in the blood stream, the bacteria can travel to the placenta, cross the placenta, and then infect a growing baby,” Abdur-Rahman says. And while typically, pregnant women don’t die from listeria — though it can cause preterm labor — there’s a 20 percent chance that it could be fatal for your baby. “The listeria bacteria has an affinity for the nervous system, so, when a developing fetus’ brain is attacked by the bacteria, death frequently results,” he explains.

Giphy

Symptoms of listeria are pretty “non-specific” for people who aren’t pregnant, and it will be just like general flu symptoms, Abdur-Rahman says. However, for pregnant people, they have more pronounced symptoms, such as “persistent headaches, a stiff neck, and even seizures or a loss of consciousness.” It is typically treated by oral antibiotics, pregnant or not. So at least treating listeria is a pretty simple procedure.

While pretty uncommon — especially in the U.S. — taking precautions against ingesting food that could potentially have listeria is a good idea while you’re pregnant, and again, that includes unpasteurized cheeses, unwashed fruits and veggies, and deli meats. As always, consult your doctor if you have any questions about what you should and should not eat while you’re pregnant. I know you miss brie and turkey sandwiches (or maybe that’s just me), but your time to eat those delicious foods will be back soon enough.

Check out Romper’s new video series, Bearing The Motherload, where disagreeing parents from different sides of an issue sit down with a mediator and talk about how to support (and not judge) each other’s parenting perspectives. New episodes air Mondays on Facebook.

Rare Disease Database

Braden CR. Listeriosis. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:290.

Ibraheem M, Vance S, Jackson KA, Ettestad P, Smelser C, Silk B. Vision Loss following Intraocular Listeriosis Associated with Contaminated Cantaloupe. Case Rep Ophthalmol. 2013 Jun 1;4(2):7-11.

Menon M, Graves L, McCombs K, Hise K, Silk BJ, Kuehnert M, Lynch M. Listeria monocytogenes in donated platelets–a potential transfusion transmitted pathogen intercepted through screening. Transfusion 2013; .

Hoelzer K, Chen Y, Dennis S, Evans P, Pouillot R, Silk BJ, Walls I. New data, strategies, and insights for Listeria monocytogenes dose-response models: summary of an interagency workshop, 2011. Risk Analysis 2013; .

Cartwright EJ, Jackson KA, Johnson SD, Graves LM, Silk BJ, Mahon BE. Listeriosis outbreaks and associated food vehicles, United States, 1998–2008. Emerg Infect Dis 2013 Jan.

Laksanalamai P, Joseph LA, Silk BJ, Burall LS, L Tarr C, Gerner-Smidt P, Datta AR. Genomic Characterization of Listeria monocytogenes Strains Involved in a Multistate Listeriosis Outbreak Associated with Cantaloupe in US. PLoS One 2012;7(7):e42448. Epub 2012 Jul 31.

Silk BJ, Date KA, Jackson KA, et al. Invasive Listeriosis in the Foodborne Diseases Active Surveillance Network (FoodNet), 2004–2009: Further Targeted Prevention Needed for Higher-Risk Groups. Clin Infect Dis 2012;54: S396–S404.

Pouillot R, Hoelzer K, Jackson KA, Henao O, Silk BJ. Relative Risk of Listeriosis in Foodborne Diseases Active Surveillance Network (FoodNet) Sites According to Age, Pregnancy, and Ethnicity. Clin Infect Dis 2012; 54: S405–S410.

Jackson KA, Biggerstaff M, Tobin-D’Angelo, Sweat D, Klos R, Nosari J, Garrison O, Boothe E, Saathoff-Huber L, Hainstock L, Fagan RP. Multistate outbreak of Listeria monocytogenes associated with Mexican-style cheese made from pasteurized milk among pregnant, Hispanic women. J Food Prot. 2011;74(6):949-53.

Jackson KA, Iwamoto M, Swerdlow D. Pregnancy-associated listeriosis. Epidemiol Infect 2010;138(10):1503-9.

Swaminathan B, Gerner-Smidt P. The Epidemiology of Human Listeriosis. Microbes Infect. 2007;9(10):1236-43.

Voetsch AC, Angulo FJ, Jones TF, et al. Reduction in the incidence of invasive listeriosis in Foodborne Diseases Active Surveillance Network Sites, 1996-2003. Clin Infect Dis 2007;44:513-20.

Gottlieb SL, Newbern C, Griffin PM, et al. Multistate outbreak of listeriosis linked to turkey deli meat and subsequent changes in US regulatory policy. Clin Infect Dis 2006;42:29-36.

Arias Miranda IM, et al., Listeriosis in the adult. Revision of 10 cases. An Med Interna. 2004;21:75-8.

Roberts AJ, Wiedemann M. Pathogen, host and environmental factors contributing to the pathogenesis of listeriosis. Cell Mol Life Sci. 2003;60:904-18.

Benshushan A, et al., Listeria infection during pregnancy: a 10 year experience. Isr Med Assoc J. 2002;4:776-80.

Pierre V, et al., Prevention of Listeria infections. Bull Acad Natl Med. 2000;184:295-302.

Schlech WF. Foodborne listeriosis. Clin Infect Dis 2000;31;770-5.

Schlech III WF. Listeria gastroenteritis – new pathogen. N Engl J Med. 1997;336:130-2
Dalton CB, et al., An outbreak of gastroenteritis and fever due to Listeria monocytogenes in milk. N Engl J Med. 1997;366:100-5.

Schuchat A, Swaminathan B, Broome CV. Epidemiology of Human Listeriosis. Clin Micro Rev 1991;4;169-83.

Linnan MJ, Mascola L, Dong Lou X, et al. Epidemic listeriosis associated with Mexican-style cheese. N Engl J of Med 1988;319:823-8.

Teberg AJ, et al., Clinical manifestations of epidemic neonatal listeriosis. Pediatr Infect Dis J. 1987;6:817-20.

INTERNET
Centers for Disease Control and Prevention. Listeriosis. www.cdc.gov/listeria Updated June 29, 2017. Accessed August 20, 2018.

Zach T. Listeria Infection. Medscape. http://www.emedicine.com/ped/topic1319.htm Updated: Jan 09, 2018. Accessed August 20, 2018.

About the author

Leave a Reply

Your email address will not be published. Required fields are marked *