Listeria is considered the deadliest foodborne illness. There have been several outbreaks in the United States in recent history, including the Jensen Farms Cantaloupes outbreak where 33 people died. Outbreaks relating to Listeria have had many different sources from dairy products, like milk, cheeses, and ice cream to frozen food items to produce.
Listeria is common in the environment. It can be found on every continent in the world and in typical places like soil, water sources, infected livestock, and maybe, your own refrigerator. The bacteria can easily survive in cold environments, which allows it to easily live in food manufacturing plants. Even after a food may have been properly heated at a manufacturing plant, cross-contamination may still occur during the final packaging process.
People become infected with Listeria through eating or drinking contaminated foods or water. According to the Centers for Disease Control and Prevention, there are several food items that are more susceptible for Listeria contamination. These food items include:
- Unpasteurized or raw milk
- Rare meat and fish
- Unpasteurized or raw milk products – like queso fresco, feta, Brie, Camembert, and blue-veined
- Raw produce which may be infected from the soil grown in or manure used to fertilize that soil
- Processed foods, like ice cream or ready-made salads
- Raw eggs and raw egg products, like homemade ice-cream and raw cookie dough
- Unpasteurized fruit juices and ciders
- Refrigerated pâtés or meat spreads
- Cold ready-to-eat meats, like deli meat, hot dogs, and sausage
- Cold ready-to-eat seafood products, like smoked salmon
- Other refrigerated smoked seafood
- Raw sprouts
Listeria infection or Listeriosis will typically go unnoticed by someone who has become infected. In healthy adults, a Listeria infection will usually remain in the digestive tract and not show any symptoms. However, healthy adults can still show symptoms and become very ill. Especially for high-risk individuals, like young children, the elderly, those with compromised immune systems, and pregnant women, Listeria can cause major issues and potentially become invasive – meaning that it can spread to other parts of the body. For instance, invasive Listeriosis could lead to a blood infection, called bacteremia or central nervous system infections, called meningitis. In pregnant women, Listeriosis may only appear to have flu-like symptoms, but can be lethal to a developing fetus or a newborn.
Pregnant women are especially at risk for Listeriosis, and are ten times more likely to become ill with Listeriosis than a non-pregnant healthy woman. The complications of Listeriosis in a pregnant woman include:
- Spontaneous abortion
- Preterm labor
- Premature birth
- Neonatal sepsis
- Neonatal meningitis
- Fatal infection after birth
The symptoms of Listeria are very alike to flu symptoms. In fact, many just assume they have the flu when in fact they have Listeriosis. Symptoms of Listeriosis can last anywhere from a few days to a few months depending on the severity of the infection and the person infected. Even though Listeriosis symptoms can be mild in healthy adults, the generalized symptoms include:
- Fever and chills
- Upset Stomach
- Abdominal pain
- Muscle aches
- Diarrhea or acute febrile gastroenteritis
Pregnant women may also experience vomiting, irritability, and fatigue.
If Listeriosis becomes more severe, the ill individual may also have the following symptoms:
- Severely high fever
- Stiff neck
- Confusion or changes in alertness
- Loss of balance
The above symptoms may be an indication that Listeriosis has spread to other parts of the body. Urgent medical attention is recommended if an individual has these symptoms.
Most healthy adults will not need treatment for Listeriosis apart from supportive care – like rest and hydration. In some instances, over-the-counter medications may be recommended by a physician. In instances where Listeriosis has become invasive, a physician may prescribe antibiotics, particularly for pregnant women.
Famous Outbreak: Between January 1, and June 14, 1985, the Centers for Disease Control and Prevention received reports of 86 cases of Listeriosis in California – 58 of these cases involved mother-infant pairs. Of the reported cases, there were 29 deaths, which included 8 fetuses, 13 stillbirths, and 8 babies. The government investigators were able to trace the infection to Mexican-style soft cheeses manufactured by Jalisco Products, Inc.