(NBC NEWS) -- An outbreak of listeria linked to Blue Bell ice cream products has been going on quietly for as long as five years, federal health officials said Tuesday.
Genetic tests link Listeria bacteria from two separate Blue Bell factories to at least six cases of listeriosis dating back to 2010, the Centers for Disease Control and Prevention told NBC News.
The outbreak, which has killed three people and put seven others into the hospital, involves two distinct strains of the bacteria that have been making people sick from Kansas to South Carolina, the CDC says.
The three exposed people who died all were in Kansas.
Blue Bell's recalled all of its products because of the outbreak, and says people should throw away any of its products in their refrigerators or freezers.