Listeria, also known as Listeriosis, is a serious infection that affects approximately 1,600 people annually in the United States, according to the Center for Disease Control and Prevention (CDC). Caused by the listeria monocytogenes bacterium, listeria is primarily found in contaminated food. Particular groups of people are at risk for developing serious illness due to listeria are the elderly, pregnant women, newborns and adults with weak immune systems.

The CDC includes listeriosis in its list of nationally notifiable diseases, which means any occurrence warrants reporting to the government. The government then tracks any outbreaks to prevent further infection through contaminated food sources. Listeria is an important public health concern, in part due to its grave effects on pregnant women and newborn children. According to the CDC, pregnant women are 20 times more likely to contract listeriosis than other adults. People with AIDS are 300 times more likely to be infected than people with normal immune systems. While adults and children who may not be at risk can be infected with listeria, the chances of developing a serious illness are very slim.

Most people with listeria experience fever and muscle aches. Because listeria is a food borne illness, it can cause gastrointestinal problems like diarrhea. The infection typically spreads beyond the digestive tract, resulting in a variety of serious symptoms. Symptoms vary according to who gets the disease. Pregnant women usually have a flu-like illness. However, listeria may cause miscarriage for women in the first three months of pregnancy. Listeriosis can also cause premature labor, a low birth weight or infant death. Pregnant women who get listeria can pass the disease onto their unborn babies through the placenta. Newborn babies suffer the worst effects of listeria, as they can develop chronic health issues such as mental retardation, paralysis, seizures, blindness or impaired functioning of their vital organs. The first sign of listeria symptoms in infants can include irritability, refusal to feed, fever and vomiting. Others who develop listeria, including older adults and people with compromised immune systems, may experience headaches, stiff neck, confusion, loss of balance or convulsions.

The bacterium listeria monocytogenes is typically found in soil, water and some animals like poultry and cattle. The bacteria contaminates a wide range of foods, including meat and dairy products. Raw, unpasteurized milk and cheeses made from this milk are particularly likely to be contaminated. Uncooked and cooked foods alike can be contaminated, such as vegetables, uncooked meats and smoked seafood. Processed meats like hot dogs and deli meats can contain the bacteria, whether they are sold over the counter or in factory-sealed packaging. While most germs stop growing in cold refrigerators, listeria continues to multiply despite the freeze. Pasteurization and thoroughly cooking food can kill listeria.

Treatment depends on the severity of the listeria. In many people, the infection presents with very few symptoms and requires no treatment. For individuals at high risk for developing listeria-related complications, listeriosis is typically treated with antibiotics. Pregnant women who take antibiotics may prevent the infection from affecting their babies. Newborn children at risk for infection may be administered antibiotics through an intravenous catheter (IV). Antibiotic treatment generally lasts 10 days.