Listeria monocytogenes is a bacterium that causes listeriosis, a serious infection. This illness can range from mild symptoms to severe, life-threatening complications, particularly for certain populations. Understanding how this bacterium is transmitted is important for prevention.
Is Direct Transmission Common?
Direct person-to-person transmission of Listeria is not a significant route of spread for the general population. Unlike common respiratory illnesses, Listeria does not typically spread through casual contact, coughing, or sneezing. The primary exception is vertical transmission from a pregnant individual to their fetus during pregnancy or to the newborn during childbirth. This specific pathway is a concern for pregnancy outcomes.
How Listeria Spreads
Listeria is predominantly a foodborne pathogen, meaning people usually become infected by consuming contaminated food. The bacterium is widely present in the environment, found in soil, water, and animal feces, which can lead to contamination of various food products. Foods can become contaminated during harvesting, processing, preparation, or storage, and Listeria has the ability to grow even at refrigeration temperatures.
Common sources of Listeria contamination include raw or unpasteurized dairy products, such as soft cheeses. Deli meats, hot dogs, and smoked seafood are also frequently implicated, especially if consumed without reheating. Produce can be contaminated from soil or animal manure, and inadequate cooking or cross-contamination can further spread the bacteria.
Who is Most Susceptible
Certain groups face a higher risk of severe listeriosis. Pregnant women are approximately 10 times more likely to contract listeriosis than other healthy adults, with potential consequences including miscarriage, stillbirth, or severe illness in the newborn. The immune system undergoes changes during pregnancy, making individuals more susceptible.
Older adults, particularly those aged 65 and above, are also at increased risk, with over half of all Listeria infections occurring in this age group. Their immune systems can become less effective, and they may have underlying chronic health conditions that compromise their defenses. Individuals with weakened immune systems due to conditions like cancer, HIV/AIDS, diabetes, kidney disease, or those on immunosuppressive medications are also highly vulnerable to serious listeriosis.
Steps to Prevent Infection
Preventing Listeria infection largely involves diligent food safety practices. Thoroughly cook raw foods, such as meats and poultry, to their recommended internal temperatures. Avoid unpasteurized milk and dairy products, opting for pasteurized alternatives. Washing raw vegetables and fruits thoroughly under running water before consumption.
To prevent cross-contamination, keep uncooked meats separate from ready-to-eat foods and wash hands, utensils, and cutting boards after handling raw ingredients. For high-risk individuals, specific precautions include reheating deli meats and hot dogs until steaming hot and avoiding refrigerated pâtés or smoked seafood unless cooked. Maintaining refrigerator temperatures at 40°F (4°C) or below helps slow Listeria in stored foods.