Listeriosis Outbreaks from Ready-to-Eat Meat Have Resumed: Why and What now?

The CDC said that when the power of PulseNet, the collaboration of federal agencies on the Listeria Initiative, and the resolution provided by GenomeTrakr were fully harnessed, we would see more outbreak cases solved, and fewer illness per outbreak. Sure enough, that is proving to be true, as once sporadic, isolated incidences of listeriosis are being linked together and detected as outbreaks. For over 15 years (2003-2017) the U.S. meat industry has had a long streak of success with no outbreaks of listeriosis attributed production of to ready-to-eat (RTE) meats in federally-inspected plants. That streak came to an end in autumn 2018 with two relatively small outbreaks from sliced ham and pork rolls of 4 cases each. On April 17, 2019, the CDC announced an investigation of another outbreak of Listeria monocytogenes illness from deli meats. As of the date of the announcement, the deli meat outbreak involves 8 cases (1 death). What is striking is the span of time of date of reported illness: November 2016 - April 2019 !

Timeline of reported cases of people infected with the outbreak strain of  Listeria monocytogenes  in Deli Meat Outbreak, by date of isolation.

Timeline of reported cases of people infected with the outbreak strain of Listeria monocytogenes in Deli Meat Outbreak, by date of isolation.

The prior two outbreaks announced in 2018 also had a small number of cases, but the span of time of illness being reported was also very long. In the Johnston County Hams, Inc. outbreak from hams, the date of isolation of the outbreak strain occurred in July 2017 and again in July 2018 through Sept 2018.

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The Long Phung Food Products, Inc outbreak spanned about the same time, from July 2017-November 2018.

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So, yes indeed we are now seeing more outbreaks and fewer cases per outbreak, but what we didn’t expect to see was such a long span of time of illness onset. This could mean that some meat processing facilities have harborages of Listeria monocytogenes in equipment or infrastructure and that its periodically getting into product. Some people like to call these, “house pets,” but they are not the friendly kind, as there’s nothing good about persistent Listeria monocytogenes in food processing plants and the same strain can reside in plants for years if not eliminated.

There are tried and true techniques to mitigate such contamination and provide effective measures to control this pathogen in meat processing plants. Get your people trained at the Listeria Control Workshop by the North American Meat Institute, and get help from experts if needed.