Government prosecutors wrapped conspiracy and fraud around the head of the former president of Blue Bell ice cream, but a hung jury did not buy it. That Texas jury was 10-to-2 in favor of acquittal.

But how then should be explained the illnesses and deaths associated with the 2015 listeriosis outbreak. Does science explain less human responsibility?

Nineteen expert researchers worked on that question, and they’ve produced a 22-page research paper with their answers. They point to an event beginning long before Blue Bell Creameries knew Listeria contamination was a threat.

The researchers hail from a long list of prestigious organizations, including the Atlanta Research and Education Foundation; the CDC Division of Foodborne, Waterborne, and Environmental Diseases; the Kansas Department of Health and Environment’s Bureau of Epidemiology and Public Health Informatics; the Texas Department of State Health Services Emerging and Acute infectious Disease Unit; the Kansas Department of Agriculture’s Division of Food Safety and Lodging; the South Carolina Department of Health and Environmental Control’s Microbiology Division; the Oklahoma Department of Health; FDA’s Center for Food Safety and Applied Nutrition; the Texas Blood Lead Surveill Branch; the Colorado Division of Disease Control and Public Health Response; Association of Food and Drug Officials, the Johnson County Department of Health and Environment, New York State’s Bureau of Epidemiology Services, and CDC’s Division of Healthcare Promotions.

The researchers note that frozen foods “have rarely been linked to listeria illnesses.”

Their outbreak investigation uses hospital clustering of illnesses and product testing. And they use “whole-genome sequencing (WGS) to look both forward and back for epidemiologic links to the listeriosis outbreak first discovered in early February 2015.

Altogether, ten illnesses and three deaths, dated from 2010 to 2015, were linked to recalled Blue Bell products. Only about 60 days of this half-decade event involved Blue Bell’s decision-making because, until early February 2015, the creamery was clueless about what was happening.

The researchers explained it this way.

“Kansas officials were investigating five cases of listeriosis at a single hospital when simultaneously unrelated sampling for a study in South Carolina identified L. monocytogenes in (Blue Bell) ice cream products made in Texas isolates four patients and (Blue Bell) were closely related by WGS, and the four patients were known exposures had consumed milkshakes made with (Blue Bell) ice cream while hospitalized.”

“Further testing identified L. monocytogenes in ice cream in a second (Blue Bell) production facility in Oklahoma; these isolates were closely related by WGS to those from five patients in three other races.”

The researchers confirmed that the outbreak was “linked” to Blue Bell ice cream products (or, as they call it, Company A). WGS and product sampling were used to link the cases spanning years and two production facilities.

The paper recommends comprehensive sanitation controls and environmental and product testing for ice cream production.

They point out that until 2014 when the Blue Bell event was occurring, that ice cream “had not been implemented as a source of listeriosis.”

The researchers acknowledged that without WGS, the outbreak likely would have gone unsolved. Instead, the new technology “helped show that seeming sporadic illnesses occurring over several years” and part of the same protracted outbreak.

“In the U.S. outbreak of listeriosis linked to a widely distributed brand of ice creme (Blue Bell), WGS and product sampling helped linked cases spanning five years at two production facilities, indicating longstanding contamination,” they said.

They conclude that the lack of regulatory oversight was responsible for the low-level contamination without detection for years. Ice cream just was not seen before then as a source of listeriosis

In total, 10 cases were reported from Kansas (5), Texas (3), Arizona, and Oklahoma, with isolation on 22  dates from January 2010–January 2015. All patients were hospitalized during the 28 days before listeriosis onset for other conditions unrelated to listeriosis; three deaths were reported.

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