The FDA has upgraded its warning about potentially deadly blueberries, indicating a ‘reasonable probability’ of serious health harms or death.

The federal agency’s update followed a recall initiated last month by Alma Pak International LLC, a produce packing facility based in Georgia, over concerns that the berries were contaminated with Listeria.

Four hundred boxes of blueberries – totaling 12,000 pounds – were shipped to a single customer in North Carolina, but it is unclear whether they were distributed elsewhere afterward.

Eating blueberries contaminated with Listeria could cause listeriosis, a potentially severe foodborne illness.

Listeria infections often begin with flu-like symptoms, including fever, muscle aches, nausea, and headache. But for vulnerable groups, the disease can be deadly.

Pregnant women face miscarriage, stillbirth, or life-threatening complications for their newborns. Older adults and immunocompromised individuals may experience severe neurological effects, including confusion, seizures, and even death.

While healthy adults usually recover, the elderly are at much higher risk of fatal outcomes due to age-related immune decline.

Four hundred boxes of blueberries – totaling 12,000 pounds – were recalled last month over listeria concerns. The FDA upgraded its warning to the public to the highest risk level

‘During routine testing the firm [Alma Pak Int’l LLC] received positive test results of Listeria monocytogenes on their finished product,’ according to the FDA.

Around 90 percent of people with listeriosis, the infection caused by listeria, require hospitalization, while 20 to 30 percent of patients die. The CDC estimates that of 1,600 cases every year, roughly 260 do not survive.

The FDA’s new risk level, Class I, ‘represents a situation in which there is a reasonable probability that the use of or exposure to a violative product will cause serious adverse health consequences or death,’ according to the FDA.

Each of the 400 boxes of blueberries weighing 30 pounds was delivered to North Carolina, but it is unclear whether that recipient was a distributor, a store, or other business, or a private individual who loves blueberries.

The FDA has not yet responded to DailyMail.com’s questions.

Blueberries are generally considered low-risk for harboring Listeria due to their low pH environment, and outbreaks linked to blueberries are rare.

Far more common are outbreaks of listeriosis linked to deli meat.

At least 61 people were hospitalized, and 10 people died of listeriosis linked to Boar’s Head deli meats last year.

Gunter ‘Garshon’ Morgenstein, a father-of-three from Newport, Virginia, is pictured above with his wife Peggy. He died after suffering from a listeria infection after eating Boar’s Head deli meats

Sue Fleming, 88, and her husband Patrick, 76, are suing deli meats manufacturer Boar’s Head and the shop where they purchased the meat after Ms Fleming became ‘deathly ill’ from listeria

The outbreak could be traced back to unsanitary conditions – including mold, insects, and liquids dripping from the ceiling – at the company’s processing plant in Jarratt, Virginia.

One victim of the outbreak was Günter Morgenstein, an 88-year-old Holocaust survivor, fell ill days after eating Boar’s Head sausage, developing Listeria-induced meningitis. He died from severe brain inflammation.

Sue Fleming, 88, and her husband Patrick, 76, are suing Boar’s Head after she ate contaminated liverwurst, leading to Listeria infection. Hospitalized for nine days in intensive care, she still suffers neurological effects and has not fully recovered.

Still, Listeria fears have caused blueberry recalls in the past as well, including one in 2022 for frozen blueberries processed in Oregon. Nobody is reported to have gotten sick.

Listeriosis can be mild in otherwise healthy individuals, but deadly in others.

In newborns, the elderly, and individuals with weakened immune systems, listeriosis can progress to life-threatening meningitis, a severe brain infection.

Between 20 and 30 percent of babies and immunocompromised people who get listeriosis will die, while between 16 and 20 percent of elderly people will die.

Symptoms of listeriosis can develop within a few days or even a few weeks after consuming contaminated food. They resemble the flu at first, with symptoms including nausea, vomiting, muscle aches, and fever.

If left untreated, the infection can progress to cause symptoms such as a stiff neck, confusion, balance problems, and seizures.

In pregnant women, listeria raises the risk of miscarriage, low birth weight, health problems for the newborn, and infant death.