Understanding Listeria: Symptoms, Prevention & When to Get Tested
Understanding Listeria
Listeria is a type of bacteria that can cause a serious infection known as listeriosis. While many healthy people may only experience mild symptoms, the infection can be dangerous for certain groups such as pregnant women, newborns, older adults, and people with weakened immune systems.
Listeria is a common foodborne illness you may have seen in the news, and it helps to know the basics to keep yourself and your family safe.
Causes of Listeria 1
Listeria can spread in food processing facilities, where they are hard to fully remove. Unlike many other bacteria, Listeria can survive and even grow in cold environments, including refrigerators. Common sources include:
- Ready-to-eat deli meats and hot dogs
- Soft cheeses made from unpasteurized milk
- Refrigerated pâtes or meat spreads
- Smoked seafood
- Unwashed raw produce
Because it thrives in cold, moist areas, Listeria can be especially tricky to prevent in food production and storage environments.
Symptoms of Listeriosis 2
There are two main types of Listeria infection: invasive and intestinal illness.
Intestinal illness: This is the milder form and can cause symptoms such as diarrhea, vomiting, fever, and muscle aches. These usually appear within 24 hours of eating contaminated food and last 1–3 days.
Invasive listeriosis: This more serious form occurs when the bacteria spread beyond the gut. Symptoms may include fever, muscle aches, stiff neck, confusion, loss of balance, or seizures. In pregnant women, it can cause flu-like symptoms but may also lead to miscarriage, premature birth, or infection in the newborn.
Risk factors for severe illness
Certain people are more likely to experience severe illness from Listeria, including:
- Pregnant women and their newborns
- Adults 65 years and older
- People with weakened immune systems (from conditions such as cancer, diabetes, kidney disease, or HIV, or from treatments like chemotherapy)
For these groups, even small exposures can lead to serious health complications.
How to prevent Listeria
You can lower your risk of infection with some simple food safety practices:
- Wash fruits and vegetables thoroughly before eating.
- Cook meat and poultry to safe internal temperatures.
- Avoid unpasteurized dairy products.
- Reheat deli meats and hot dogs until steaming hot.
- Keep refrigerators at or below 40°F and freezers at 0°F.
- Clean your refrigerator regularly, especially areas where leaks or spills may occur.
Outbreaks of foodborne illness 3
When two or more people get the same illness from the same contaminated food or drink, the event is called a foodborne disease outbreak. Public health officials investigate outbreaks to control them, so more people do not get sick, and to learn how to prevent similar outbreaks from happening in the future.
Recalls are when a company voluntarily or involuntarily pulls product. This could be due to a bacterial contamination, such as Listeria, foreign object contamination, issues with labeling or packaging, or undeclared allergens.
To check if there is a current recall, visit the HHS Food Safety website, which shows recalls and public health alerts from both the FDA and USDA.
Choose HNL Lab Medicine 
Most people with mild intestinal illness from Listeria recover without testing. But if symptoms last longer than expected or become more severe, it’s important to rule out other causes.
Our comprehensive testing menu, trusted accuracy, and fast results give you and your healthcare provider the clarity you need. With more than 50 convenient locations and a team dedicated to quality care, HNL Lab Medicine makes it simple to take the next step in protecting your health.
REFERENCES
¹ Centers for Disease Control and Prevention. (2024, August 12). How listeria spreads. U.S. Department of Health and Human Services. https://www.cdc.gov/listeria/causes/index.html .
² Centers for Disease Control and Prevention. (2025, February 03). Symptoms of listeria infection. U.S. Department of Health and Human Services. https://www.cdc.gov/listeria/signs-symptoms/index.html.
³ Centers for Disease Control and Prevention. (2025, March 17). Listeria outbreaks. U.S. Department of Health and Human Services. https://www.cdc.gov/listeria/outbreaks/index.html.