skip to main content

Public Health - Seattle & King County


Listeriosis is an infection caused by the bacteria Listeria monocytogenes. Persons at increased risk for severe infections include immunocompromised persons, the elderly, pregnant women, and newborn infants. The bacterium is unusual among foodborne pathogens in that it multiplies at low temperatures, including in refrigerated foods. Transmission occurs primarily through ingestion of contaminated drinks and foods, including raw (unpasteurized) or contaminated milk, soft cheeses such as queso fresco, vegetables, and ready-to-eat meats. During pregnancy, infection can lead to spontaneous abortion, stillbirth, or premature birth. Transmission during delivery can cause severe, often fatal, infections in the newborn, even if the mother is asymptomatic.

Resources for the general public
Resources for health care providers
Listeriosis in King County

Purpose of surveillance:

  • To identify common source outbreaks
  • To identify and eliminate sources of transmission, including contaminated food products

Listeriosis case reports

Local epidemiology:

Seven cases of listeriosis were reported in 2013, including one mother-infant pair. All cases were hospitalized, and none died. Four cases occurred among persons who were immunocompromised, two cases were pregnant (one of which resulted in fetal demise) and one was a perinatally infected infant who survived.

Washington state has received 12 to 25 reports of listeriosis per year during recent years.