How Deadly is Listeria?

You might not even know you have it. Listeria is a sneaky little bug that can cause a serious foodborne illness called listeriosis. It's especially dangerous for pregnant women, newborns, the elderly, and people with weakened immune systems.

Listeria monocytogenes is a type of bacteria that causes listeriosis, a serious infection primarily caused by consuming contaminated food. Although it's not one of the most common foodborne illnesses, Listeria has a reputation for being particularly dangerous, especially for vulnerable groups. The high mortality rate associated with listeriosis, as well as its ability to survive in harsh conditions, makes it a deadly pathogen worthy of attention. In this blog, we will explore how deadly Listeria truly is, who is most at risk, and what can be done to prevent this illness.

What is Listeria?

Listeria monocytogenes is a gram-positive bacterium found in soil, water, and decaying plant material. It can also inhabit certain animals without causing illness, thereby contaminating meat, dairy, and produce. Unlike many bacteria, Listeria can thrive in cold environments, making it a significant concern in refrigerated foods such as deli meats, soft cheeses, and ready-to-eat meals. Once inside the human body, it invades the gastrointestinal tract, sometimes spreading to other parts of the body, causing serious complications.

Listeriosis, the infection caused by Listeria, can manifest in a range of symptoms depending on the individual's health and immune status. While many people might experience mild flu-like symptoms, for others, particularly those with weakened immune systems, listeriosis can lead to severe complications and even death.

Who is Most at Risk?

Listeriosis is particularly dangerous for specific groups of people, including:

 

1. Pregnant women: Pregnant women are about 10 times more likely to get listeriosis than the general population. While the mother may only experience mild symptoms, the infection can have devastating consequences for the fetus. Listeria can cross the placental barrier, leading to miscarriage, stillbirth, or severe illness in newborns.

   

2. Newborns and Infants: Newborns who contract Listeria from their mothers are at high risk for severe complications, including life-threatening infections like sepsis and meningitis.

3. Older adults: The immune system weakens with age, making people over 65 more susceptible to Listeria infections. This age group is also more likely to have underlying conditions like diabetes or heart disease, which can further increase the risk of severe illness or death.

4.People with weakened immune systems: Those with compromised immune systems due to conditions such as HIV/AIDS, cancer, diabetes, liver or kidney disease, or those on immunosuppressive therapies (like chemotherapy) are particularly vulnerable to listeriosis. Their bodies have a reduced capacity to fight off the infection, which can lead to the bacteria spreading beyond the gastrointestinal tract.

5. Individuals on certain medications: Immunosuppressive drugs and medications like steroids, which dampen immune responses, also heighten the risk of severe complications from Listeria.

For these at-risk groups, the infection can result in bacteremia (bacteria in the blood), meningitis (inflammation of the brain and spinal cord membranes), or other severe health outcomes. The mortality rate for invasive listeriosis is high, ranging from 20% to 30%, even with prompt treatment.

Symptoms of Listeriosis

Listeria infections can present differently depending on the severity of the infection and the individual’s health status.

•  In healthy adults, the symptoms are usually mild and may resemble the flu. These can include:

  - Fever

  - Muscle aches

  - Nausea and vomiting

  - Diarrhea

Most healthy individuals recover without complications, often without even knowing they have contracted Listeria.

• In high-risk individuals (pregnant women, older adults, and those with weakened immune systems), the symptoms can escalate into more serious conditions:

  - Severe headaches

  - Stiff neck

  - Confusion

  - Loss of balance

  - Convulsions

  

These symptoms are indicative of Listeria spreading to the central nervous system, which can lead to meningitis or encephalitis, both of which are potentially fatal if left untreated.

Pregnant women may experience mild, flu-like symptoms, but the real concern lies in the risk to the fetus or newborn, where stillbirth or neonatal death is a serious threat.

How Does Listeria Become Deadly?

The lethality of Listeria is due to several factors, including the following:

1. Invasive Nature of the Bacteria: Listeria is capable of penetrating the body’s natural barriers, such as the gastrointestinal lining, and can spread through the bloodstream to the brain, spinal cord, or placenta. This invasive ability increases its potential for causing life-threatening conditions like meningitis, encephalitis, and septicemia.

2. High Mortality Rate: When Listeria infection spreads beyond the gastrointestinal system (known as invasive listeriosis), it can be deadly. Even with treatment, 20-30% of invasive listeriosis cases result in death. Pregnant women, newborns, the elderly, and immunocompromised individuals have a much higher risk of death from this infection.

3. Ability to Thrive in Cold Environments: Listeria can grow in refrigerated conditions where most bacteria cannot. This makes foods like deli meats, soft cheeses, and pre-packaged salads particularly risky, even if stored at the right temperatures.

4. Antibiotic Resistance: Though rare, some strains of Listeria have developed resistance to antibiotics, complicating treatment efforts. While Listeria infections are generally treated with antibiotics like ampicillin and gentamicin, resistance could pose a problem in some cases.

How Deadly is Listeria Compared to Other Foodborne Illnesses?

Listeria may not be as common as other foodborne pathogens like Salmonella or E. coli, but it is deadlier. While the CDC estimates there are only about 1,600 cases of listeriosis in the U.S. each year, about 260 of those cases result in death. This is a high mortality rate compared to other foodborne illnesses.

For example, in the case of Salmonella, which causes approximately 1.35 million infections in the U.S. annually, only about 420 result in death. Although Listeria cases are far less common, the bacteria’s ability to cause severe infections and death, particularly in vulnerable populations, makes it significantly more lethal on a case-by-case basis.

Prevention of Listeriosis

Given the high mortality associated with Listeria, prevention is critical. Here are some key strategies for reducing the risk of listeriosis:

1. Practice good food hygiene: Wash fruits and vegetables thoroughly under running water. Make sure to clean all surfaces and utensils that come into contact with raw food, especially when preparing food for high-risk individuals.

2. Cook food thoroughly: Listeria is killed by cooking at temperatures of 165°F (74°C) or higher. Make sure meats, poultry, and other potentially risky foods are cooked properly.

3. Avoid risky foods: High-risk groups should avoid foods that are more likely to be contaminated with Listeria, including:

   - Unpasteurized milk and dairy products

   - Deli meats unless reheated to steaming hot

   - Soft cheeses such as Brie, Camembert, and blue-veined cheeses unless labeled as made with pasteurized milk

   - Prepackaged or store-prepared deli salads

4. Refrigerate food properly: Listeria can grow at refrigerator temperatures, so it’s essential to keep perishable foods chilled at 40°F (4°C) or lower. Regularly clean your refrigerator and throw out expired or suspicious food.

5. Pay attention to recalls: Food recalls due to Listeria contamination are not uncommon. Keep up to date with food safety announcements and avoid consuming any recalled products.

Conclusion

Listeria is indeed a deadly pathogen, particularly for pregnant women, newborns, the elderly, and individuals with compromised immune systems. Although it is not the most common foodborne illness, its high mortality rate and invasive nature make it a significant public health concern. The good news is that listeriosis is largely preventable with the right food safety practices. By staying informed and taking the necessary precautions, the risk of infection can be minimized, and vulnerable populations can be better protected from this potentially lethal bacterium.

Be healthy, Thank you