Listeriosis cases being investigated in western Washington

Listeriosis cases that have hospitalized five people and killed three are being investigated in western Washington.

The Tacoma-Pierce County Health Department is working with the Washington State Department of Health and Thurston County Public Health and Social Services to investigate the cases. A common food source has not yet been identified, according to a statement on the state health department’s website.

Four of the cases are in Pierce County, with one in Thurston County. All the cases were in patients with weakened immune systems in their 60s or 70s.

Investigators are interviewing patients or their proxies to help identify any common exposures.

Genetic fingerprinting results (whole genome sequencing) indicate the patients likely have the same source of infection, according to the Washington State Department of Health statement. Patients became ill between February 27 and June 30.

Listeriosis is an infection caused by the bacteria Listeria monocytogenes. Those most at risk are people with weakened immune systems or who are pregnant, the newborn or the elderly.

Washington sees 10-25 cases each year, according to the Tacoma-Pierce County Health Department.

Symptoms usually develop between three to 70 days after exposure, with about half of those infected developing symptoms within 3 weeks.

To protect yourself from listeriosis:

• Avoid unpasteurized or raw milk or food made from unpasteurized milk.
• Thoroughly cook raw meat like beef, pork or poultry.
• Wash raw vegetables well before eating.
• Keep uncooked meats away from vegetables and from cooked or ready-to-eat foods.
• Wash hands, knives and cutting boards after handling uncooked foods.
• Eat perishable and ready-to-eat foods as soon as possible.

People most at risk of infection should avoid:

• Unpasteurized soft cheeses like queso fresco and brie.
• Unheated hot dogs, lunch meats or deli meats.
• Refrigerated pates or meat spreads.
• Refrigerated smoked seafood, unless it is in a cooked dish like a casserole.
• Leftover foods or ready-to-eat foods unless heated or reheated to steaming hot before eating.
• Premade deli salads like potato, tuna or chicken salad, or coleslaw.
• Getting fluid from hot dog packages on other foods, utensils, and food preparation surfaces.