Cheese-associated outbreaks of human illness in the United States, 1973 to 1992: sanitary manufacturing practices protect consumers.

To identify contributing factors for cheese-associated outbreaks, we reviewed all cheese-associated outbreaks of human illness reported to the Centers for Disease Control and Prevention (CDC) with onsets during 1973 to 1992. The infrequency of large, cheese-associated outbreaks was notable because such outbreaks had been a frequent public health problem before the mid-20th century. Of 32 reported cheese-associated outbreaks, 11 attributed to manufacturing errors caused most of the illnesses and hospitalizations and all 58 deaths. Important factors in these 11 outbreaks were manufacturing cheese with raw or improperly pasteurized milk and postpasteurization contamination. If current Food and Drug Administration sanitary requirements for cheesemaking had been met, these outbreaks would have been preventable. In two outbreaks of Salmonella infections, fewer than 10 Salmonella per 100 g of cheese were detected. In two outbreaks of Brucella infections, efforts to recover the pathogen from the implicated cheese were unsuccessful, emphasizing the inadequacy of end product testing for assuring consumer safety. Curing cheeses kills most bacteria present in cheeses; however, evidence from sources other than the CDC Foodborne Disease Outbreak Surveillance System suggests that curing alone may not be a sufficient pathogen control step to eliminate Salmonella, Listeria, and E. coli O157:H7 from cheese.