The Curious Case of Walnut-Based Brie That Caused an Epidemic in Multiple States

Real brie cheese in Paris.
Enlarge / Real brie cheese in Paris.

Niche plant-based foods are often touted for their health benefits, but one benefit that may be less obvious is that they can help prevent disease outbreaks from spreading.

This was the case of a small Salmonella epidemic from late 2020 to early 2021, described Thursday in a study published by the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report. The outbreak involved an unusual plant-based food that carried unusual bacteria. And from just two cases, health officials could identify the source and trigger a product recall before standard outbreak measures kick in, crushing an outbreak that could have spread across the country.

The food at the center of the outbreak was cashew brie โ€” an alternative to vegan brie โ€” and the first two cases identified were in Tennessee. Both people said they ate the same brand of cashew brie at the same restaurant before falling ill. And the clinical isolates found they had the same rare serotype of Salmonellaโ€”S Duisburg. Health officials sequenced the entire genome of the offending bacterium and entered them into a national repository of pathogen isolates collected for disease surveillance. There were three genetically linked matches: two isolates from California and one from Florida.

Initial follow-up determined that one of the California patients also confirmed eating the same brand of cashew brie, while Florida health officials noted that their patient reported following a vegan diet. This was enough to bolster the initial hypothesis that the vegan cheese was the culprit, and state and federal health officials got to work to solve the case.

dirty nuts

Disease sleuths collected 36 samples linked to the suspected fake brie: 20 retail cheese samples and 16 environmental samples taken from the production facility where the vegan cheese was made. Of the 20 samples sold at retail, 19 were found to be contaminated with Salmonella (95 percent), as well as four of 16 environmental samples from the production facility (25 percent). In the face of overwhelming evidence, cashew brie maker Jule’s Foods issued a voluntary recall.

The Food and Drug Administration worked with Jule’s on a traceback to determine how the Salmonella snuck into their soft cheese substitute. The ultimate source turned out to be the star ingredient of the product: cashews. Raw cashews used for cheese have not undergone “lethality treatment” such as pasteurization or irradiation before being processed. The FDA worked with the cashew supplier to resolve this issue.

While many nuts in the United States are sold as “raw”, they are often not entirely raw. Instead, they use steam, fumigation, or another method to kill dangerous pathogens. This isn’t always the case, as the cashew brie outbreak demonstrated, but it often is. For example, in 2007, after Salmonella outbreaks were linked to almonds, the US Department of Agriculture implemented a rule that California almonds – which account for the entire commercial supply of almonds in the US – must be treated to kill Salmonella.

Ultimately, with the Salmonella strain linked to cashew brie samples, state and federal health officials identified just 20 cases in four states during the outbreak. Although five people were hospitalized, there were no deaths.

Health officials noted in the MMWR report that “rapid detection, investigation and product recall prevented additional illnesses, given the detection of Salmonella in 95% of cashew brie products collected from retail outlets during this survey. ยป

If, by any chance, this is the first time you have learned of the existence of cashew cheese, you are late. It’s been around for a while – in fact, long enough to have sparked another small Salmonella outbreak in 2014. This outbreak was linked to another brand of cashew cheese and it affected 17 people in three states.

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