Listeria Hysteria: Food Recalls Grow As Bacteria Sickens Fewer People

Photo Credit: Scott Bauer (USDA)

Listeria hysteria seems to be sweeping the nation as food recalls pop up everywhere.

If you haven't kept track of the recent recalls caused by the potentially lethal bacteria, here's a recap:

• 47 million pounds of vegetables with meat were just recalled from popular stores in the United States
• All that recalled food stemmed from a recall of 15 different frozen vegetable products in April
• Dole recalled packaged salads from an Ohio processing facility in March
• Jensen Farms in Colorado recalled whole cantaloupes linked to 33 deaths in 2012
• Blue Bell Creameries ice cream was recalled after consumers were hospitalized in 2015

If you think there's been a spike in listeria-related recalls in recent years, you're right, according to Elliot Ryser, professor of food science at Michigan State University.

But the increase in recalls is actually a sign that food safety measures are getting better, not worse. And, more specifically to listeria, the bacteria is sickening fewer people than ever before.

Improving detection and prevention

As Ryser explained, our technology for detecting outbreaks has improved. "The CDC [Centers for Disease Control] has gone to what they call 'whole-genome sequencing' to identify Listeria and other pathogens. It's more sensitive than what we've used in the past," he said.

In other words, listeria hasn't become more common, but we're better at finding it and preventing further contamination.

Recalls, after all, are one sign that our management of the food supply is working. If recalls never happened, that would probably mean that contamination events were ignored or undiscovered.

"The number of cases of listeriosis has dropped quite dramatically since the 1990s," Ryser said. "The estimate back then was 2,500 cases a year, and now we're down to about 1,500 cases a year."

Pregnant women, elderly people and people with compromised immune systems are most vulnerbale to listeria. While listeriosis can be deadly, the vast majority of people who become infected will recover.

Ryser said the drop in outbreaks has largely come from changes in the "ready-to-eat meat" industry. Packaged meats are now commonly pasteurized and formulated to prevent the growth of listeria.

In fact, deli-prepared meats, according to Ryser, are seven times more likely to contain listeria.

Where does listeria come from?

Listeria is found in the natural environment, especially soil, where it can be easily transferred to foods, Ryser said. In food processing plants, the bacteria can contaminate equipment and preparation surfaces, spreading to countless products.

This is why the recalls often include so many products, costing companies millions of dollars, not to mention consumer confidence. When a case of listeria contamination is discovered, many millions of pounds of food might have already passed through the equipment in question.

Companies themselves test for the presence of listeria in their facilities, but the Food and Drug Administration and the United States Department of Agriculture also conduct tests that can lead to recalls. The United States has a zero-tolerance policy regarding listeria, which means no amount of the bacteria can be present in ready-to-eat foods.

No other country has a zero tolerance policy for listeria in food preparation environments. Some will allow anywhere from 100 to 1,000 cells to be found without recalling a product, as long as its a type of food in which listeria cannot easily grow, according to Ryser.

Until recently, there had been a serious debate in the United States about whether or not regulations should be relaxed on products such as ice cream. Experts believed it was very unlikely for listeria to thrive in these kinds of foods, so a higher level of of the bacteria could be tolerated.

That debate essentially ended, Ryser explained, after the outbreak of listeriosis in people who had eaten Blue Bell ice cream. With consumers in the hospital, it became clear that listeria still posed a real danger even in foods thought to be low-risk. In Ryser's view, this means the zero-tolerance policy for listeria is here to stay.