Cause: Bacterium Listeria monocytogenes.

Illness and treatment: Diarrhea occurs but is not detected with standard stool culture methods. Complications include septicemia or meningitis, which cause fever, headache, vomiting, delirium, or coma. Severe infections are treated with antibiotics.

Sources: Listeria occur in soil, water, and the intestines of animals and humans. Transmission is mainly through food, such as unpasteurized milk, cheese made from unpasteurized milk, processed meats, deli salads, fruits and vegetables. Food can be contaminated during or after processing.

Additional risks: Unlike most foodborne pathogens, Listeria can multiply in refrigerated foods. Illness may be severe for newborns, the elderly, and persons with weakened immune systems. Pregnant women with listeriosis may have few symptoms but have fetal loss or premature birth.

Prevention: If pregnant or immunocompromised, avoid soft cheeses made with unpasteurized milk, processed ready-to-eat foods, and smoked fish. Also thoroughly cook all foods from animal sources, wash raw produce thoroughly and heat leftovers, hot dogs and deli meats until steaming before eating.

Recent Washington trends: Each year there are 11 to 29 reports with 0 to 5 deaths.

Purpose of Reporting and Surveillance

  • To identify outbreaks and related cases.
  • To identify sources of contaminated food products and prevent further transmission from such sources.
  • To determine the public health impact of sources of contaminated food products.

Legal Reporting Requirements

  • Health care providers and Health care facilities: notifiable to local health jurisdiction within 24 hours.
  • Laboratories: notifiable to local health jurisdiction within 24 hours; submission required – isolate or if no isolate specimen associated with positive result, within 2 business days. Specimen submission is required – isolate (2 business days).
  • Local health jurisdiction: notifiable to the Washington State Department of Health (DOH) Communicable Disease Epidemiology (CDE) within 7 days of case investigation completion or summary information required within 21 days.