A deadly outbreak of infections from Listeria is under investigation by state and local officials in Washington.

As of late today five patients had been identified. All five required hospitalization and three have died, according to the Tacoma-Pierece County Health Department.

All of the patients are or were in their 60s or 70s and all had weakened immune systems, according to the health department, which is working with Washington State Department of Health (DOH) and Thurston County Public Health and Social Services.

The Tacoma News is reporting that “genetic fingerprinting results (whole genome sequencing) indicate that these patients likely have the same source of infection. Patients became ill between February 27 and June 30, 2023.”

State and local public health officials have not yet discovered a source for the bacteria. They are interviewing patients and their representatives to develop a profile.

The state of Washington generally logs 10 to 25 cases of Listeria infection annually, according to the Tacoma health department.

About Listeria infections
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has developed symptoms of Listeria infection should seek medical treatment and tell their doctors about the possible Listeria exposure.

It can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop. 

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.