Pasteurized milk a culprit in disease.

Bacteria in pasteurized milk from a Massachusetts supermarket chain two years ago caused an outbreak of listeriosis, a rare, often fatal infection, researchers from the Centers for Disease Control report in the Feb. 14 NEW ENGLAND JOURNAL OF MEDICINE. It is the first time bacteria have been found to have escaped the pasteurization process and cause human illness.

The bacteria showed up in pasteurized milk, the researchers say, because they are highly resistant to heat. Their numbers were great enough to cause infection because many cows at farms supplying milk to the diary were infected. Inspectors found the only dairy involved in the incident to be clean and modern. They say it had processed the milk correctly.

The findings suggest that pasteurization may not always be 100 percent effective in removing disease-causing bacteria from milk, according to the researchers. However, their report notes, "it is important to remember the potential benefits of this food product and the amount of human illness caused by consumption of unpasteurized milk" (SN: 2/9/85, p. 88).