Remember the listeria outbreak of 2011? Cantaloupe was the culprit in what was one of the worst foodborne illness outbreaks in U.S. history. It might've been enough to turn you off that fragrant fruit for a while, or forever.
More recently, Sargento cheese, organic pesto, edamame, and frozen burritos have all been recalled for possible listeria contamination, and federal health officials are investigating a listeria outbreak tied to soft raw cheeses from an artisanal New York producer.
How worried should you really be about listeria? How likely are you to get sick from it? And is there anything you can do to avoid it? We've got the answers.
What is listeria?
It's a foodborne bacteria, full name Listeria monocytogenes.
It tends to lurk in deli meats and hot dogs, unpasteurized soft cheeses, and refrigerated smoked seafood. Past listeria outbreaks have also been linked to raw sprouts, frozen vegetables, celery, caramel apples, and hummus.
How does listeria get into food?
The bacteria is naturally present in soil and water, so fruits and vegetables can get contaminated in the field. Animals can carry listeria, too, infecting meat and dairy products.
There's also a risk of contamination in facilities where foods are processed and prepared. Listeria is fond of moisture and can grow in drains or wherever there's pooling water.
"It could be something where it came in on somebody's shoe and gets established in the processing environment," says Amanda Deering, clinical assistant professor in the Department of Food Science at Purdue University. (Her most recent research found that listeria can live inside the tissue of romaine lettuce.)
It spreads through contact like any germ. What's especially troubling is that unlike other bacteria, listeria can survive—and multiply, albeit slowly—in refrigeration.
However it finds its opening, "once it's there, it's pretty hard to get rid of," Deering says.
How do I know I've eaten something that's contaminated?
If you're a relatively healthy adult, you might never know. It can take a few days or as many as two months for symptoms to show. You could get a fever, headache, or diarrhea or feel a general malaise for a short time, and then get better, and that's it.
But listeria infection (also called listeriosis), which is confirmed by a lab culture and treated with antibiotics, can be serious, even fatal, for pregnant women, infants, the elderly, and people with weak immune systems. Symptoms often start out flu-like but can lead to meningitis in listeria's oldest and youngest victims and to miscarriage, stillbirth, or infection of a newborn in pregnant women, according to the Centers for Disease Control.
How common is listeria infection?
It's nowhere near as prevalent as salmonella or E.coli, but it's more deadly, especially for those who are most at risk.
The CDC estimates 1,600 people get sick from listeria every year and 260 die. By contrast, of the more than 1 million salmonella cases annually, about 450 die.
How do I avoid listeria infection?
Should I just not eat hot dogs? And lox? And melon? No, no, and no (that is, unless you already have an aversion to those foods). The key thing to know is that heat kills listeria, so cook your meat and produce thoroughly.
Then again, hot cantaloupe—who likes that? So you also have to accept that certain foods have a higher risk of contamination than others, and take precautions at home to reduce the spread of foodborne germs in general.
That means washing produce before using—scrub that melon, and eat or chill it immediately once cut, cleaning your fridge and kitchen surfaces often and well, making sure your fridge and freezer are cold enough (at or below 40 and 0 degrees, respectively), and washing your hands often while cooking, per CDC and FDA recommendations.
If you are among those most susceptible to getting really sick—again, that's pregnant women, babies, the elderly, and the immunocompromised—it's best to fully cook or choose shelf-stable cooked versions of those high-risk foods, or avoid them altogether.