What is listeriosis?

Listeriosis is an illness caused by the bacterium Listeria monocytogenes. This organism can be found normally in soil and water, and in silage (an animal feed). Illness due to Listeria typically occurs as sporadic cases, however several outbreaks have been recognized in recent years.

Who gets listeriosis?

Anyone can become infected with Listeria monocytogenes, however the disease primarily affects pregnant women, newborns, the elderly and people with weakened immune systems. In the United States, about 1,100 persons become seriously ill with listeriosis each year. In New Jersey, about 20 cases are reported each year. One-third of all cases happen during pregnancy.

How is listeriosis spread?

Outbreaks of listeriosis have been associated with raw (unpasteurized) or contaminated milk, soft cheeses, contaminated vegetables, and ready-to-eat meats. A substantial proportion of the sporadic cases are also likely to be caused by food-borne transmission. Listeriosis can also be transmitted to an unborn child during pregnancy or during childbirth. Infected animals can also be a source of listeriosis.

What are the symptoms of listeriosis?

Listeriosis can affect different body organs and thus cause a variety of symptoms. Usual symptoms include fever, muscle aches and sometimes nausea or diarrhea. If the infection involves the nervous system, it may cause headaches, stiff neck, confusion and/or convulsions. Pregnant women with listeriosis may experience only mild flu-like illness. However, listeriosis during pregnancy often leads to premature delivery, infection of the newborn, or stillbirth.

How soon do symptoms occur?

Symptoms generally occur about three weeks after coming into contact with Listeria monocytogenes, however it may be as short as 3 days or as long as 2 months.

How is listeriosis diagnosed?

Listeriosis is diagnosed by testing the blood or spinal fluid for the Listeria monocytogenes bacterium.

What is the treatment for listeriosis?

There are several antibiotics that are effective against this bacterium. However, infections of the central nervous system can be fatal despite treatment with appropriate antibiotics. Early diagnosis and rapid institution of appropriate antibiotic therapy is critical for a successful recovery.

How long is an infected person infectious to others?

Listeriosis is not spread from person-to-person.

How can listeriosis be prevented?

Good sanitary practices are the best methods to prevent listeriosis and other food-borne illnesses. The following are good general guidelines:

• Thoroughly cook raw food from animal sources, such as beef, pork, or poultry.
  
• Wash raw vegetables before eating.
  
• Keep uncooked meats separate from vegetables, cooked meats, and ready-to-eat foods.
  
• Avoid raw (unpasteurized) milk.
  
• Wash hands, knives, and cutting boards after handling uncooked foods.

In addition to the above, persons at high risk, such as pregnant women and persons with weakened immune systems may wish to take the following additional precautions:

• Avoid soft cheeses such as feta, Brie, Camembert, blue-veined, and Mexican-style.
  
• Cook left-over or ready-to-eat foods such as hot dogs until steaming hot.
  
• Although the risk of listeriosis associated with cold cut meats from deli counters is relatively low, pregnant women and immunosuppressed persons may wish to avoid them, or thoroughly heat them before eating.

More about listeriosis

• Surveillance Case Definitions
• Centers for Disease Control