Historically, U.S. dairies have not worried themselves about the possibility of pathogens in their products.
In 1985, an outbreak of Listeriosis was traced to Mexican style cheeses being produced in a Los Angeles plant that was bypassing the pasteurizer. The California outbreak, along with a Salmonella outbreak in Chicago, and additional Listeria scares elsewhere tarnished the "pure and safe" image of dairy. The industry needed to react. But how?