Listeria infection is an illness caused by bacteria that can spread through many foods. Another name for the illness is listeriosis. It can be very serious for pregnant women, people older than 65 and people with weakened immune systems. Some foods are more likely to be tainted by the bacteria than others. These include soft cheeses, deli meats and dairy products that haven't been treated to kill bacteria, called pasteurized.

Healthy people rarely become very ill from listeria infection. But the disease can be fatal to unborn babies, newborns and people with weakened immune systems. Prompt antibiotic treatment can help curb the effects of listeria infection.

Listeria bacteria can survive refrigeration and even freezing. So if you're at higher risk of serious infections, be mindful of what you eat. Stay away from foods that are more likely to contain listeria bacteria.

Symptoms of a listeria infection partly depend on where in the body that the infection happens. If it affects the gut, you might have:

• Loose stools, called diarrhea.
• Upset stomach.
• Vomiting.

These symptoms often start within a day of eating tainted food. They tend to go away within a few days.

The germs that cause a listeria infection also can spread through the blood and into the brain and spinal cord. If this happens, you might have:

• Fever and chills.
• Flu-like symptoms such as muscle aches and fatigue.
• Diarrhea or an upset stomach.
• Headache.
• Stiff neck.
• Confusion or changes in alertness.
• Loss of balance.
• Seizures.

These symptoms often start within two weeks of eating tainted food. But it can take up to two months for symptoms to begin.

Symptoms during pregnancy and in newborns

During pregnancy, a listeria infection is likely to cause only mild symptoms in the pregnant person. But the effects on the baby can be devastating. The baby can die in the womb or have a life-threatening infection within a few days of birth.

Symptoms of a listeria infection in a newborn can be subtle. But they can include:

• Little interest in feeding.
• Crankiness.
• High temperature, called fever, or low temperature, called hypothermia.
• Vomiting.
• Trouble breathing.
• Little to no energy.
• Low birth weight.

If you've eaten a food that's been recalled because of a listeria outbreak, watch for symptoms of illness. Call your healthcare professional if you have a fever, muscle aches, upset stomach or loose stools. The same goes for illness after eating foods that might be tainted. These include foods made with unpasteurized milk or poorly heated hot dogs or deli meats. Let your healthcare professional know what you ate.

Get emergency care if you have any of the following:

• A high fever.
• Very bad headache.
• Stiff neck.
• Confusion.
• Discomfort or pain due to light.

These could be symptoms of a life-threatening condition that can happen with a listeria infection, called bacterial meningitis.

Listeria bacteria can be found in soil, water and animal waste, also called stool. People can get infected by eating the following:

• Raw vegetables that have been tainted from the soil or the manure used as fertilizer.
• Tainted meat.
• Raw milk or foods made with unpasteurized milk, also called unpasteurized products.
• Certain processed foods such as soft cheeses, hot dogs and deli meats that have been tainted after processing.
• Cold-smoked fish such as nova or lox.
• Sprouts.
• Melons.

Pregnant people with listeria infections can pass the infections to their unborn babies. This is a risk even if a pregnant person doesn't have symptoms of the infection.

Pregnant women, people older than 65 and people with weak immune systems are at highest risk of a listeria infection.

Pregnant women and their babies

Pregnant women are much more prone to listeria infections than are other healthy adults. A listeria infection might cause only a mild illness in pregnant women. But the risks include:

• Miscarriage.
• Stillbirth.
• Premature birth.
• A life-threatening infection in the baby after birth.

People who have weakened immune systems

This includes people who:

• Are older than 65.
• Have conditions such as cancer, diabetes, kidney or liver disease, autoimmune diseases, alcohol use disorder, and HIV or AIDS.
• Get chemotherapy to treat cancer.
• Take high-dose steroid medicines.
• Take treatments that lower the immune system. Examples include some medicines for rheumatoid arthritis and medicines to block rejection of a transplanted organ.

Many listeria infections are mild. Some infected people don't have any symptoms. But sometimes, a listeria infection can lead to serious medical problems or emergencies. These risks rise if treatment is delayed or not given.

A listeria infection of the bloodstream can cause the body to have an improper reaction called sepsis. This can lead to organ damage or death.

A listeria infection of the nervous system can lead to:

• Trouble with balance, walking or coordination.
• Trouble moving one side of the body.
• Nerve problems.
• Hearing loss.
• Seizures.
• Death.

Babies with life-threatening listeria infections of the blood or brain might develop lifelong conditions such as:

• Intellectual disabilities.
• Paralysis.
• Seizures.
• Blindness.
• Conditions that affect the brain, kidneys or heart.

To prevent a listeria infection, follow simple food safety guidelines:

• Keep things clean. Wash your hands with warm, soapy water before and after you handle or prepare food. Scrub well for at least 20 seconds. After you cook, use hot, soapy water to wash the utensils, cutting boards and other surfaces you prepared food on.
• Scrub raw vegetables. Clean raw vegetables with a scrub brush or vegetable brush under plenty of running water. Do this before you eat, peel, cut or cook the vegetables.
• Do not rinse raw meat or poultry. This helps prevent bacteria from spreading to other surfaces in the kitchen.
• Cook your food thoroughly. Use a food thermometer to make sure your meat, poultry and egg dishes are cooked to a safe temperature.
• Refrigerate food. This helps keep perishable foods from spoiling. Set your refrigerator temperature to 40 degrees F or below. Keep your freezer at 0 degrees F or lower.

Precautions for people particularly at risk

If you're pregnant or you have a weak immune system, be extra cautious about listeria. Take added safety measures with these types of foods:

• Soft cheeses and Mexican-style cheeses. Don't eat these, even if they were made using pasteurized milk. Some examples of soft cheeses are feta, brie, Camembert and blue cheese. Mexican-style cheeses include queso blanco and queso fresco.

• Hot dogs and deli meats. Stay away from these unless they're reheated until steaming hot. Keep fluid from hot dog packages away from other foods, utensils and surfaces on which food is prepared. Wash your hands after handling these products.

  Use any opened hotdog packages in the refrigerator within one week. Use closed packages within two weeks. When you refrigerate lunch and deli meats or meat sliced at your deli, use opened packages within 3 to 5 days. Use closed packages of factory-sealed lunch and deli meats within two weeks of storing in the refrigerator.

• Meat spreads. Don't eat refrigerated meat spreads sold at a deli or meat counter, or from a store's refrigerated section. Canned meat spreads are OK. So are shelf-stable spreads, which can be safely stored at room temperature. Refrigerate after opening though.
• Smoked seafood. These products can be labeled as nova style, lox, kippered or jerky. It's OK to eat them in cooked dishes. Canned or shelf-stable smoked seafood also is OK.
• Raw or lightly cooked sprouts. Cook sprouts of any kind thoroughly.
• Cut melon. Eat the fruit right away or refrigerate it. Keep it refrigerated at 41 degrees Fahrenheit or lower, and use it within seven days. Throw out any cut melon that's left at room temperature for over four hours.
• Raw milk or milk products, also called unpasteurized milk. Do not use these at all. Only use pasteurized milk and milk products. Make sure the product's label says "pasteurized."

Often, healthcare professionals do a blood test to find out if you have a listeria infection. Samples of spinal fluid might need to be tested as well. If you're pregnant, the fluid that surrounds your baby during pregnancy also might be tested.

Treatment of listeria infection varies. It depends on how serious the symptoms are. Most people with mild symptoms don't need treatment. More-serious infections can be treated with medicines that clear up infections caused by bacteria. These are called antibiotics.

During pregnancy, prompt antibiotic treatment might help keep the infection from affecting the baby.

If you've eaten food that has been recalled because of listeria contamination, be aware of listeria infection symptoms. See a healthcare professional if you have any of the symptoms.

What you can do

Before your checkup, write a list that answers the following questions:

• What are your symptoms and when did they start?
• Are you pregnant? If so, how far along are you?
• Are you being treated for other medical conditions?
• What medicines and supplements do you take?

You also might want to write a food diary. List all the foods you've eaten for as far back as you can remember. Tell your healthcare professional if foods you've eaten have been recalled.

What to expect from your doctor

Your healthcare professional might ask if you've recently eaten:

• Soft cheeses, such as brie, Camembert or feta.
• Mexican-style cheeses, such as queso blanco or queso fresco.
• Raw milk or cheeses made of raw milk, also called unpasteurized milk.
• Processed meats, such as hot dogs or deli meats.
• Any foods that have been recalled.