At least six pregnant women contracted a fatal infection after eating vegan cheese contaminated with listeria, scientists say, while another person suffered brain damage.
Four of the women had a premature birth, a fifth suffered a septic infection and an infection in a sixth expectant mother spread to her fetus and caused brain swelling.
Researchers in France revealed the outbreak and warned that it suggested alternative vegan products may not be safer than basic dairy products.
Lactose-free products are often considered safer and healthier because they do not contain dairy, which can be contaminated with dangerous bacteria and microbes.
But the researchers cautioned that the products had not gone through processes such as pasteurizationwhich would normally kill any dangerous microbe.
Six pregnant women were affected by the listeria outbreak in several European countries (stock)
Listeria outbreaks by year in the US, as shown in this chart from the CDC
The cases were revealed in a letter sent to New England Journal of Medicine.
Scientists at France’s Pasteur Institute wrote: “This outbreak highlights the lack of data on contamination of [vegan] products from foodborne pathogens, and the need for manufacturers of vegan cheese substitutes to consider this risk in their production processes, as with any other ready-to-eat product.
Researchers eventually traced listeria to the Jay and Joy brand of vegan cheese, which is not available in the U.S. The cheeses were sold in 1,900 stores nationwide.
Cases were also detected in Belgium, Germany and the Netherlands, and a Europe-wide alert was issued about the contamination.
This is believed to be the first time vegan cheeses have been linked to listeria, and researchers say it may be because the products used raw nut milk.
Nuts can become contaminated with listeria in fields if they are exposed to water mixed with animal feces.
During the manufacturing process, nuts are not pasteurized like traditional dairy products, which researchers say left room for listeria to survive and infect humans.
Listeria outbreaks are often reported linked to dairy products, including cheeses, and are likely to become contaminated after coming into contact with surfaces infected with listeria.
In February of this year, the CDC warned of a listeria outbreak in cheese sold at Whole Foods: It found that two Americans had died and 23 people had been hospitalized in 11 states.
In the United States, the FDA has not yet detected any listeria outbreaks linked to vegan foods, including those containing nuts.
But it has already detected outbreaks of salmonella bacteria associated with cashews or cashew-based products.
Salmonella can also be transmitted through nuts if they are exposed to water contaminated with animal feces.
Most people exposed to listeria suffer a mild illness with symptoms including fever, muscle aches and vomiting that disappear within five days.
But those who are most at risk, including the elderly and pregnant women, may suffer a more severe illness due to their weakened immune system called listeriosis.
This infection is rare but very serious: According to the CDC, about 20 to 30 percent of patients die from the disease. More than 90 percent of infected patients are hospitalized.
The outbreak in Europe was linked to Jay and Joy vegan cheese, pictured above.
Complications of the infection include meningitis (or inflammation of the brain) and sepsis (a life-threatening overreaction of the immune system) if the bacteria enter the blood.
Approximately 1,600 Americans become ill with listeria each year, while approximately 260 patients do not survive the infection.
The outbreak in France affected eight people in total, including a three-year-old child, and was reported between April and December 2022.
Four of the pregnant women gave birth at 32 weeks, eight weeks earlier than what is considered a full-term pregnancy of 40 weeks.
No deaths were recorded as a result of the outbreak.
Cases are commonly linked to the consumption of poorly processed sausages or unpasteurized dairy products, rather than vegan cheeses.
The listeria in these meats can survive stomach acid and infect the intestines causing a disease called listeriosis.