A foodborne illness caused by Listeriosis monocytogenes has infected five people in Pierce and Thurston counties, killing three, according to the Washington State Department of Health.
All of them are older than 60 and have compromised immune systems, the department noted. They were infected between Feb. 27 and June 30.
The Department of Health, the Tacoma-Pierce County Health Department and Thurston County Public Health and Social Services are leading the investigation.
After using whole genome sequencing and examining fingerprints, investigators determined the patients likely had the same source of infection. A common food source has not been confirmed though, the Department of Health said.
Listeria bacteria can spread from contaminated food onto surfaces. It can be killed by heating up food to around 165 degrees Fahrenheit.
The illness is especially harmful to people who are over 65 years old, have weakened immune systems or are pregnant.
Symptoms can include fever, muscle aches and fatigue. They usually begin within two weeks of eating contaminated food, but they can start instantly or sometimes 10 weeks after exposure.
