Niche plant-based foods are often touted for their health benefits—but one benefit that may be less obvious is that they can help keep outbreaks from mushrooming.

Such was the case with a small Salmonella outbreak from late 2020 to early 2021, outlined 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 starting with just two cases, health officials could identify the source and spur a product recall before standard outbreak measures were triggered—squashing an outbreak that could have festered across the country.

The food at the outbreak's center was cashew brie—a vegan brie alternative—and the first two cases identified were in Tennessee. The two people reported eating the same brand of cashew brie at the same restaurant before falling ill. And clinical isolates found they had the same rare serotype of Salmonella—S. Duisburg. Health officials conducted whole genome sequencing of the offending bacteria and entered them into a national repository of pathogen isolates collected for disease surveillance. There were three genetically related matches: two isolates from California and one from Florida.

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

Dirty nuts

Disease detectives collected 36 samples related to the suspect faux brie: 20 retail samples of the cheese and 16 environmental samples collected from the production facility where the vegan cheese was made. Of the 20 retail samples, 19 were found tainted with Salmonella (95 percent), as were four of the 16 environmental samples from the production facility (25 percent). Facing the overwhelming evidence, the cashew brie maker, Jule's Foods, issued a voluntary recall.

The Food and Drug Administration worked with Jule's on a traceback to nail down how the Salmonella sneaked into their soft-cheese substitute. The ultimate source turned out to be the product's star ingredient: cashews. The raw cashews used for the cheese didn't go through a "lethality treatment" such as pasteurization or irradiation before being processed. The FDA worked with the cashew supplier to fix this.

While many nuts in the US are sold as being "raw," they're often not entirely raw. Rather, they go through steaming, fumigation, or some other method to kill off dangerous pathogens. This isn't always the case, as demonstrated by the cashew brie outbreak, but it often is. For instance, in 2007, after Salmonella outbreaks were linked to almonds, the US Department of Agriculture implemented a rule that Californian almonds—which account for the entirety of the commercial almond supply in the US—must be treated to kill off Salmonella.

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

The health officials noted in the MMWR report that "rapid detection, investigation, and product recall prevented additional illnesses, given the detection of Salmonella in 95 percent of cashew brie products collected at retail locations during this investigation."

If, by chance, this is the first you're learning of the existence of cashew cheese, you are behind the times. It has been around for a while—in fact, long enough to have sparked another small Salmonella outbreak in 2014. That outbreak was linked to a different brand of cashew cheese, and it affected 17 people in three states.