(NEWSnet) — Three people are dead and two others are in the hospital after contracting listeria in Washington state.

According to the Washington State Department of Health, the outbreak came from an unknown food source all five likely contracted it from. It's still unknown what the food source is.

All the infected patients were older than 60, and each had a compromised immune system, the Washington Department of Health said. 

The bacteria can be found on food preparation surfaces, fresh, unpasteurized cheese, leafy greens and cold cuts. 

Those infected with listeria report flu-like symptoms for one to four weeks after eating contaminated food.