According to press reports this morning, the pasteurization process at Whittier Farms, the central Massachusetts dairy connected to a deadly outbreak of a bacterial illness, appears to be working properly. Dr. Alfred DeMaria, the state director of communicable disease control, said that could mean the listeria bacteria that sickened four people, killing 2 adults and an unborn child in Massachusetts, entered Whittier Farms’ milk supply after it was pasteurized. DeMaria said the Massachusetts outbreak is believed to be just the third ever in pasteurized milk in the United States.

Three seemed low to me, so I spent a few hours today surfing the web looking for other outbreaks of bacterial or viral illnesses that have been tied to pasteurized milk or milk products. What I was able to find from other sources and a CDC chart summarizing Pasteurized Milk Outbreaks by State and pathogen – 1966 – 2000. I did not find any other outbreaks tied to pasteurized milk or milk products (although lots from unpasteurized).  So, if anyone has some, I will add them to the chart.

What is evident from the below chart (and reading the literature on each outbreak) is that in each instance the cause of the outbreak was either inadequate pasteurization, post-pasteurization contamination or unknown. So, I suppose in some ways these are all really unpasteurized milk outbreaks?

Date –  Location   –   Species   –   Cases

1966 – Florida – Shigella flexneri – 97

1975 – Louisiana – Salmonella Newport – 49

1976 – New York – Y. enterocolitica – 38

1978 – Arizona – S. Typhimurium – 23

1979 – UK – Campylobacter jejuni – 3,500

1982 – Tenn., Ark., Miss. – Y. enterocolitica – 172

1983 – Massachusetts – Listeria monocytogenes – 49

1984 – Kentucky – S. Typhimurium – 16

1985 – Illinois – S. Typhimurium – >150,000

1986 – Vermont – Campylobacter jejuni – 35

1992 – UK – Campylobacter jejuni – 23

1992 – UK – Campylobacter sp. – 110

1994 – Illinois – L. monocytogenes – 45

1995 – UK – Campylobacter sp. – 12

1995 – Vermont, New Hampshire – Y. enterocolitica – 10

1999 – UK – E. coli O157:H7 – 114

2000 – Pennsylvania, New Jersey – S. Typhimurium – 93

2004 – Denmark – E. coli O157:H7 – 25

2005 – Colorado – Campylobacter jejuni – 40

2006 – California – Campylobacter jejuni – 1,644

Foodsnark sent me this interestingly, disturbing find:

Fatal Bacteria May Have Survived Pasteurization
from the Los Angeles Times from 1985:

The bacteria found in Mexican-style cheese and linked to 31 deaths in Southern California possess an unusual ability to live as parasites inside the white blood cells of animals and humans where they may be protected from the heat of the pasteurization process, scientists at the federal Centers for Disease Control believe.

Mycobacterium avium Subspecies paratuberculosis has been shown to survive in retail milk that had been pasteurized in the United Kingdom and the United States and shows that humans are being exposed to this chronic enteric pathogen by this route. There appears, however, to be insufficient scientific evidence to prove a link between Johne’s disease (or MAP) in animals and Crohn’s disease in humans.

Any more articles on bacteria and viruses surviving pasteurization?

  • Bill:
    Pasteurized milk receives a lethality treatment intended to make the milk safe. The outbreaks listed are examples of outbreaks in pasteurized milk. Infrequent outbreaks indicate that pasteurized milk or milk subject to a lethality treatment is rarely the cause of illness. Process failures at the pasteurization step and post lethality contamination are simply uncontrolled hazards in the milk production process. Which from a food safety point of view, does not make pasteurization any less important but illustrates in any lethality treatment, other uncontrolled process steps can lead to hazardous foods. The raw milk industry should not gloat about this outbreak in pasteurized milk. Raw milk advocates should be reminded about the inherent hazards in all diary products and question even more the safety of un-pasteurized milk.
    Roy Costa
    Public Health Sanitarian

  • Tom Youngblood

    Pennsylvania has 87 PA Dept. of Ag. permitted raw milk producers.
    In the 80’s my department sampled pasteurized milk in retail stores monthly and often found SPC’s in the millions with multiple days until the “sell by” date. No efforts, however, were made to identify the bacteria.
    Tom Youngblood
    Health Officer
    Meadville, PA

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