Listeria Infection – Symptoms and Causes
What You Need to Know About Listeria
What You Might Catch and How to Avoid It
Listeria is a foodborne illness caused by bacteria. It can be dangerous for certain groups of people. While healthy individuals rarely get sick from listeria, it poses serious risks to pregnant women, adults over 65, and those with weak immune systems.
The infection comes mainly from eating poorly processed deli meats and dairy products that haven’t been pasteurized.
What makes listeria tricky is that the bacteria can survive in cold temperatures, even in your refrigerator or freezer. If doctors catch the infection early, antibiotics can help fight it. However, for high-risk individuals, avoiding certain foods is the best protection.
People at higher risk should be careful about what they eat to prevent this potentially life-threatening infection, especially since it can be deadly for unborn babies and newborns.
Signs and Symptoms
Pregnancy and Newborn Symptoms
Listeria infection during pregnancy often causes mild symptoms in the mother but can be dangerous for the unborn child. The baby might die before birth or develop a serious infection shortly after being born.
A pregnant woman might experience:
- Fever
- Chills
- Muscle aches
- Nausea
- Diarrhea
Symptoms may appear within days of eating contaminated food but could take up to 30 days to develop.
When listeria spreads to the nervous system, additional symptoms include:
- Headache
- Stiff neck
- Confusion
- Balance problems
- Seizures
Newborns with listeria infection may show subtle signs such as:
- Poor feeding interest
- Unusual irritability
- Fever
- Vomiting
- Breathing difficulties
These symptoms in babies require immediate medical attention as the infection can be life-threatening. Early treatment is essential for improving outcomes in affected newborns.
When to See a Doctor
Contact your doctor if you develop fever, muscle aches, nausea or diarrhea after eating:
- Food that has been recalled due to listeria
- Products made with unpasteurized milk
- Poorly heated hot dogs
- Deli meats
Seek emergency medical care immediately if you experience:
- High fever
- Severe headache
- Stiff neck
- Confusion
- Sensitivity to light
These serious symptoms might indicate bacterial meningitis, which is a dangerous complication of listeria infection. This condition requires prompt medical attention.
Causes
Listeria infections mainly come from bacteria found in soil, water, and animal waste. People typically get sick from eating:
- Raw vegetables grown in contaminated soil or fertilized with infected manure
- Meat carrying the bacteria
- Unpasteurized (raw) milk and products made from it
- Processed foods like soft cheeses, hot dogs, and deli meats that become contaminated during production
For pregnant women, the infection can pass to their unborn babies through the placenta. This makes pregnancy a particularly risky time for listeria exposure.
Who Is at Risk
Pregnant Women and Unborn Babies
Pregnant women face much higher risks of listeria infections compared to others. While the mother might only experience mild symptoms, the consequences for the baby can be severe:
- Miscarriage
- Stillbirth
- Early delivery
- Life-threatening infection after birth
Pregnant women should be especially careful about food choices and preparation to protect themselves and their developing babies.
People with Weakened Immune Systems
Several groups have higher risk due to compromised immune function:
| High-Risk Groups | Reasons |
|---|---|
| Adults over 65 | Natural immune decline with age |
| People with AIDS | Compromised immune response |
| Cancer patients receiving chemotherapy | Reduced white blood cell counts |
| Those with diabetes or kidney disease | Impaired immune function |
| People taking certain medications | Including high-dose prednisone, transplant rejection drugs, or specific arthritis medications |
These individuals should take extra precautions with food safety to prevent infection.
Complications
Listeria infections often go unnoticed due to mild symptoms. However, some cases become serious and can threaten lives. Two main complications include:
- Bloodstream infection – bacteria can spread throughout the blood
- Meningitis – inflammation develops in the protective membranes and fluid around the brain
These severe complications require immediate medical attention.
Safety Steps for High-Risk People
Preventing listeria infection involves simple food safety practices.
Wash your hands with warm, soapy water before and after handling food.
Clean all cooking surfaces, utensils, and cutting boards with hot, soapy water after each use.
Always wash raw vegetables thoroughly under running water using a vegetable brush. This helps remove bacteria that might be on the surface.
Make sure to cook all foods to safe temperatures.
Use a food thermometer to check that meat, poultry, and egg dishes reach the proper internal temperature.
If you’re pregnant or have a weakened immune system, you need to be extra careful about certain foods:
Cheese cautions:
- Avoid soft cheeses (feta, brie, Camembert, blue cheese)
- Skip Mexican-style cheeses like queso blanco and queso fresco
- Only eat these if they clearly state “made with pasteurized milk”
Meat safety:
- Don’t eat hot dogs or deli meats unless heated until steaming hot
- Keep hot dog package fluid away from other foods and surfaces
- Wash hands after handling these products
- Avoid refrigerated meat spreads (canned or shelf-stable options are safer)
Seafood guidance:
- Don’t eat refrigerated smoked seafood (labeled as nova style, lox, kippered, jerky)
- These are safe when used in cooked dishes
- Canned or shelf-stable smoked seafood is acceptable
Sprout safety:
- Always cook sprouts thoroughly before eating
- Raw or lightly cooked sprouts pose a risk
Following these guidelines helps reduce your risk of getting sick from listeria bacteria.
