by Katherine Brind’Amour, PhD
When people talk about listeria or listeria symptoms, they are often referring to the infection caused by Listeria bacteria. This infection is technically called listeriosis, and it affects about 1,600 people per year in the United States, according to the Centers for Disease Control and Prevention (CDC). (1) Although most people who come into contact with listeria don’t get sick, the infection can be deadly. About 1 in 5 people who develop invasive listeriosis (meaning it spreads from the gut to places like the blood or brain) die from it. (2)
People with healthy immune systems who eat food contaminated with listeria usually don’t get sick. If they do, their listeria symptoms are usually mild. However, exposure to contaminated food can lead to a serious infection in people with weak immune systems, people over the age of 65, pregnant women and the fetus, and infants. (3)
In many cases, you can prevent illness caused by listeria. Read on to learn more about this illness, listeria symptoms, and natural ways you can prevent and recover from listeria infections.
What Is Listeria?
Listeria monocytogenes is a bacterium (germ) that can cause an infection called listeriosis (casually referred to just as “listeria”). In most cases, listeria infection happens after someone eats a food that has the bacteria on it. Each year, about 1,600 people in the U.S. get sick from listeria and about 260 of them die from their infections. (4)
Most people fight off listeria without even feeling sick. But in pregnant women, even a mild infection for the mother can be bad news for the fetus. About 1 in 5 cases of listeriosis during pregnancy causes the death of the fetus, through stillbirth or miscarriage. (5) In cases where the baby is born alive, about 3 percent die as newborns because of the listeriosis infection passed from the mother during pregnancy. (6)
Food preparation standards and surveillance programs have reduced the frequency of contaminated foods at grocery stores and restaurants. Thankfully, that has made outbreaks less common than they were in the past. (7) It is hard to track the true number of outbreaks because of the delay between when people eat the contaminated food and when they have listeria symptoms — as well as the fact that many people have no symptoms at all. The CDC reports that a few true outbreaks of listeria happen almost every year in the U.S. (8)
When listeriosis is invasive, it can lead to serious infections in the blood or brain, as well as other organs, such as the heart. (9) When the infection affects the spinal fluid, it causes swelling and inflammation of the brain and spinal cord (called meningitis). When it spreads to the blood, listeriosis can cause sepsis, or bacteremia. It is this type of invasive infection in the blood or organs that is most likely to cause serious outcomes, such as miscarriage or death.
Symptoms of Listeria monocytogenes food poisoning can start the same day after eating contaminated food. However, some people do not have symptoms for as many as 70 days. Most people who become sick from listeria have symptom onset within one to four weeks of eating affected food. (10)
Food poisoning usually causes fever, diarrhea or vomiting, but these are rarely the signs of listeria. So what are the symptoms of listeria infection? Most people with diagnosed listeriosis have problems beyond tummy troubles. This happens when the infection becomes invasive.
Symptoms of listeria infection that has spread past the gut (invasive listeriosis) include: (11)
- Flu-like symptoms, such as feeling very tired (fatigue) or having achy muscles
- Stiff neck
- Joint pain
- Dizziness or loss of balance
- Convulsions (being shaky or having seizures)
Listeria in pregnant women most often causes flu-like symptoms and fever. However, it can have other very serious outcomes, such as miscarriage, stillbirth, premature delivery, or a dangerous infection or death in her newborn. (12) Even if the mother has only mild listeria symptoms, the infection can pass to the baby.
Symptoms of listeria infection in babies can be hard to identify since many babies who are infected have serious complications (like a blood or brain infection) by the time they get to the doctor. (13) In some cases, the infection is obvious right away (usually when the baby has a low birth weight and has other signs of illness around birth). In others (usually when the baby is born seemingly healthy), there can be a delay of several weeks before the infection is apparent. (14) Early signs of a listeria infection in a baby who was previously healthy can include: (15)
- Lack of interest in feeding
If you, your infant or someone you know has listeria symptoms and had a possible exposure to contaminated food, seek care from a medical professional. Let them know that a listeria infection could be a possibility and why. For example, tell them if you ate food that was recalled due to an outbreak.
Causes & Risk Factors
Most often, listeria symptoms occur after people have eaten food contaminated with listeria bacteria. In addition, pregnant women who get the infection can pass it to the fetus through the placenta. (16)
A combination of factors causes a full-blown listeria infection. First, someone has to eat or ingest the listeria bacteria. Then, the person’s immune system must fail to kill the bacteria in the stomach or gut. The bacteria then reproduce and spread inside the intestines, making people feel sick. If the bacteria spread to the blood, spinal fluid or other organs, the infection can be very serious and even life-threatening.
Most healthy people do not get listeria symptoms, even after exposure, because their body is able to fight off the bacteria by itself. People whose immune systems cannot kill the bacteria are at the greatest risk of an infection.
Risk factors for listeriosis include:
- Being pregnant: Pregnant women are 10 times more likely to get listeriosis than other people. (17)
- Being Hispanic and pregnant: Hispanic pregnant women have 24 times the risk of other people of getting listeriosis, likely because soft cheeses that are popular in the Hispanic community are a common source of listeria contamination. (18)
- Being a fetus or newborn of a woman who had listeriosis during pregnancy.
- Being 65 or older: More than half of all listeriosis cases each year happen in older adults, who are four times more likely than others to get the illness. This is because the immune system weakens with age, stomach acid decreases with age, and older people are more likely to have other health problems or to be taking medications that weaken their immune system. (19)
- Having a health problem that weakens the immune system, such as cancer, diabetes, HIV/AIDS, another chronic illness, or another infection. (20)
- Taking a medication that weakens the immune system: Drugs such as steroids, chemotherapy, TNF-antagonists, and certain other medications can suppress or reduce the ability of your immune system to fight infection as it normally would. (21)
- Eating foods that commonly carry listeria: These foods include soft cheeses such as brie or feta, deli meats and hot dogs, and other ready-to-eat refrigerated foods. (22)
- Eating food that was recalled due to listeria contamination: If you ate something that was later recalled and you have symptoms of listeria infection within two months, tell your health care professional. (23)
Listeria infection is caused by the Listeria monocytogenes bacterium and diagnosed with a laboratory cell culture test. This bacterial culture is done using a sample of the person’s body fluid or tissue — most often through blood or spinal fluid, or a sample of the placenta.
Serious listeria infection is treated with antibiotics. The exact drug and the treatment regimen will depend on a number of factors. For example, a doctor will consider the patient’s age, how sick they are, where the infection is found in the body, any personal drug allergies, and whether the patient is pregnant.
The recommended antibiotics for listeria treatment include ampicillin and gentamicin, in cases where the brain or blood are involved. (24) Other options may include trimethoprim/sulfamethoxazole, meropenem, imipenem/cilastatin, vancomycin, ciprofloxacin or amoxicillin. (25) Treatment takes at least two weeks (and up to six), depending on which drugs are given and where the infection is found in the body.
10 Natural Methods for Listeriosis Prevention & Recovery
Obviously, it’s best to avoid this food-borne illness altogether. Try to prevent infection using the tips below. If you do have mild listeria symptoms and are not considered high-risk, the recovery tips below may also help.
Prevent It Naturally
There are several natural, easy ways that people at high-risk can prevent listeriosis:
- Avoid the most common contaminated food sources: (26, 27)
- Unpasteurized milk and cheeses. While raw milk has many health benefits, it’s important that it comes from a reputable, safe source and is consumed within the appropriate timeframe. However, if you’re pregnant or at high-risk for listeriosis, it’s best to avoid unpasteurized dairy products.
- Soft, fresh cheeses (such as queso fresco, queso blanco, brie, Camembert or feta) unless they are labeled as made with pasteurized milk
- Ice cream
- Deli meats and hot dogs
- Raw meats or fish
- Raw or lightly cooked sprouts (such as alfalfa, mung bean, radish or clover sprouts)
- Eat food from reputable suppliers: (28)
- Foods that have been prepared with proper food safety practices are very unlikely to be contaminated with listeria
- Reputable suppliers will keep food properly refrigerated and have strict cleanliness standards for their kitchen and prep surfaces
- Follow proper food preparation practices: (29)
- Wash your hands before touching and after food that you are going to prepare or eat.
- Clean kitchen counters, knives, bowls, cutting boards, sink, colander and other prep spaces/tools before use.
- Do not share — or, be sure to clean between the use of — spaces/tools for different foods (for example, wash the knife and cutting board if you are first cutting raw chicken and then cutting vegetables for a raw veggie platter).
- Clean up any spills in the refrigerator or on prep surfaces, especially juices from meat.
- Stop bacteria by refrigerating and heating food properly: (30)
- Cook meat, seafood and sprouts thoroughly to kill bacteria.
- Heat deli meats or hot dogs to steaming before eating them.
- Use refrigerated, fresh-cut deli meats within three to five days; factory-sealed lunch meats can be stored, refrigerated and unopened, up to two weeks.
- Cover and refrigerate leftovers within two hours and eat within three or four days.
- Refrigerate or eat cut melon (and other fruits and vegetables) within four hours, and do not keep longer than seven days.
- Keep your refrigerator temperature at 41 F or colder and your freezer at 0 F or colder.
- Spread the word:
The best ways to recover from listeria symptoms will depend on the type of infection you have and how serious it is. Severe cases require antibiotics and a hospital stay. Milder cases in non-pregnant adults, however, can be treated naturally at home.
These natural treatments can help you recover from mild food poisoning (such as diarrhea, fever, fatigue and muscle aches) caused by listeria bacteria:
- Rest: Take it easy until your symptoms subside.
- Hydrate: Even small sips of water or an electrolyte drink, such as coconut water, will help your body replenish fluids.
- Eat a bland diet: Focus on toast, bananas, rice and other bland foods until you feel up to a regular diet.
- Use heat or cold: Soothe aching muscles with a heating pad or ice pack for 15 minutes at a time.
- Treat your fever: Take a lukewarm bath or try these other natural ways to reduce a fever.
Do not ignore symptoms of listeria while pregnant, even if the symptoms are mild. Pregnant women and others who are at high risk for listeria infection should always be alert for the key listeria symptoms. The symptoms can be confused with other health problems or even overlooked in some cases. But listeriosis can lead to serious complications that can be deadly in people with risk factors. If you think you may have listeriosis during pregnancy, talk to a doctor right away. This will give you and your baby the best chance of avoiding the worst side effects.
Even if you are not in a high-risk group, talk with a health professional if you think you ate a food contaminated with listeria. Do not attempt to self-diagnose if you have symptoms. Even if you do not require medical care, you may help alert public health professionals to a possible outbreak. This could help others.
Although listeriosis is not the most well-known type of food-borne illness, it can be serious, especially for people who are pregnant, newborn, elderly or have a weakened immune system. Because its symptoms are hard to recognize, listeria infection may be underdiagnosed. Most people can fight it off without any illness, or with only mild symptoms, while for others — particularly unborn or newborn babies — the infection can be deadly.
If you think you may have listeriosis, or if you may have eaten food contaminated with listeria, talk to a health professional. Be vigilant about the key listeria symptoms: fever, muscle aches, fatigue, confusion, stiff head and neck, joint pain or convulsions. Seek care right away if you are high-risk and have any of these symptoms or if you think listeria infection may be causing mild symptoms. The earlier you receive care, the more likely you can nip the infection in the bud. And remember, you may help others do the same if your infection is due to contaminated food that others also may have eaten.
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