What is listeria? And why is it attacking ice cream?

Earlier this week Jeni’s Splendid Ice Cream, an award-winning artisanal ice cream company (because, yes, you can win awards for ice cream), announced that it would be destroying more than 535,000 pounds of the cold treat after its products tested positive for listeria.

The news came after Blue Bell ice cream recently recalled products due to listeria contamination that led to the deaths of three people. And in the last four months, three other ice creameries have all pulled products because of listeria.

So clearly, the question begs: What the hell is listeria, and what does it have against ice cream?

What is listeria?

Listeria monocytogenes is a food-borne pathogen that can (clearly) be very harmful to humans—though it’s only been causing outbreaks since the 1980s. It’s basically a pathogenic millennial.

Listeria is particularly dangerous because symptoms of listeria infections (also known as listeriosis) are subtle and can be hard to track. While other food-borne bacteria like salmonella and E. coli can cause significant gastrointestinal distress within 6 to 24 hours, listeria rarely causes gastrointestinal problems, and it takes a week or two for symptoms to manifest. Symptoms include fever, muscle aches, and a stiff neck, and in very rare cases, diarrhea.

To better understand how listeria works, Fusion called up Arun Bhunia, professor of food science at Purdue University’s College of Agriculture. “It manages to get into the blood circulation quickly, and moves to the liver, spleen, and even the brain,” Bhunia said. “It particularly affects those with a compromised immune system, elderly people, and pregnant mothers.”

More common than you think

Despite the recent attention listeria is getting, listeria-related recalls are actually are not that rare. The U.S. Department of Agriculture has announced 21 recalls due to possible listeria contamination since 2012, and Bhunia said that outbreaks leading to human infections have occurred about once a year for the past four years. Listeriosis is generally treatable with antibiotics.

“It’s such a common outbreak. There are many food-borne pathogens. If you look at the CDC and the FDA, they repeatedly report recalls, and product recalls are so common,” Bhunia said. “Ready-to-eat meat products like hot dogs, frankfurters, deli meats, smoked fish are at a high risk.”

Pasteurize to prevent future contamination

So how does ice cream come into play? Well, dairy products are also susceptible to listeria.

“It can come through milk and other dairy products. Other organisms cannot survive at such low temperatures, but listeria can survive and sometimes even grow,” Bhunia told Fusion. “The only thing is to make sure the milk has been properly pasteurized.”

Pasteurization, for those of you who don’t know, is basically when milk is passed through a high heat treatment (about 161°F or 280°F for “ultra-pasteurized”) for a short period of time (between 15 seconds and .5 seconds) to kill off bacteria.

But even if the milk product is pasteurized, Bhunia said, listeria can develop in food processing plants, and there are countless potential sources of the bacteria: the floor, the air conditioning unit, even the people handling the food.

Jeni’s found listeria in its production kitchen—and of course, production is on hiatus until the company is 100 percent certain it’s listeria free. Blue Bell, currently third in U.S. ice cream sales, is still investigating the source of its outbreak with no plans for resuming production yet.

Sweating the small business stuff

“The entire ice cream industry is on notice,” CDC food borne disease expert Rob Tauxe recently told Bloomberg. But for small businesses like Jeni’s, which is set to lose $2.5 million over the recall, that notice has a huge impact.

“As a small batch ice cream producer who has innovated the ice cream market in so many ways, Jeni’s has set the bar high, from her triple bottom line labor practices to her sourcing to her culinary craft…It is scary to see something this debilitating happen to someone you respect,” Jennie Dundas, co-founder and CEO of Brooklyn-based Blue Marble ice cream, said to Fusion in a statement. (Full disclosure: My roommate works for Blue Marble.)

“I have faith that consumers will be able to see through this challenge and welcome Jeni’s back onto the shelves once her issue is resolved,” Dundas said.

When it comes to her own business, Dundas will continue taking the same precautions as usual, “working with our local Department of Agriculture to ensure absolute food safety in all our manufacturing processes.”

As for us consumers, the fact that a few ice creameries have been hit with listeria does not mean that all ice cream is doomed. For now.