What to know
- Listeria bacteria can cause an infection called listeriosis.
- Signs and symptoms of listeriosis depend on the person infected, and the body part affected.
- Listeria are most likely to harm pregnant people, newborns, older adults, and people with weakened immune systems.
- Other people can be infected with Listeria, but they rarely become seriously ill.
![Listeria Illustration of Listeria monocytogenes bacteria under a microscope.](/listeria/media/images/2024/04/listeria.jpg)
Invasive illness
"Invasive" means bacteria have spread beyond the intestines (gut). Invasive listeriosis happens when Listeria spreads beyond the intestines.
Symptoms of invasive illness usually start within 2 weeks after eating food contaminated with Listeria.
Symptoms of invasive illness
People who are pregnant
Symptoms typically include
- Fever
- Flu-like symptoms, such as muscle aches and fatigue
People who are not pregnant
Symptoms typically include
- Fever
- Flu-like symptoms, such as muscle aches and fatigue
- Headache
- Stiff neck
- Confusion
- Loss of balance
- Seizures
Severity of invasive illness
People who are pregnant
- Symptoms in pregnant people are usually mild. Some pregnant people never have symptoms.
- However, infection during pregnancy usually leads to
- miscarriage,
- stillbirth,
- premature delivery, or
- life-threatening infection of the newborn.
- miscarriage,
People who are not pregnant
- Symptoms in non-pregnant people can be severe.
- Almost 1 in 6 non-pregnant people with invasive listeriosis die.
Intestinal illness
Listeria can also cause an intestinal illness. This kind of illness is rarely diagnosed because laboratories do not regularly test patient samples for Listeria.
Symptoms of intestinal illness usually start within 24 hours after eating food contaminated with Listeria and usually last 1–3 days.
Symptoms of intestinal illness
Symptoms typically include:
- Diarrhea
- Vomiting
Severity of intestinal illness
- Symptoms are usually mild.
- However, some people with intestinal illness develop invasive illness.
When to talk to your doctor
Contact a healthcare provider if both of the following things apply to you:
- You ate food that has been recalled or linked to an outbreak.
- You have a fever and other symptoms of listeriosis, such as fatigue and muscle aches.
Let the healthcare provider know if you ate possibly contaminated food. This step is especially important if you are pregnant, are 65 years or older, or have a weakened immune system.
If you ate food possibly contaminated with Listeria and do not feel sick, most experts believe you do not need tests or treatment. Talk with a healthcare provider if you have questions about what to do.