The Agriculture Department announced Tuesday that meat producer BrucePac was recalling 11.8 million pounds of ready-to-eat meat and poultry products due to possible listeria contamination, just months after the listeria-related recall of Boar’s Head deli meats in July.
With two major recalls of listeria-laden food in just the past few months, many may be wondering what listeria is, what the risks are and how to avoid infection.
Here’s what to know.
What is listeria?
Listeria monocytogenes is a type of bacteria that can contaminate food and cause serious complications for certain groups of individuals.
Specifically, pregnant women, newborns, adults over age 65 and people with weakened immune systems should watch out for this bug, which can lead to miscarriage, widespread infection, inflammation of the brain and spinal cord lining, muscle pain, and flu-like symptoms.
In healthy adults, it can cause watery diarrhea.
The bacteria often spread in deli meats, unpasteurized dairy products and soft cheeses. It can also spread in smoked fish, ice cream, and raw or processed vegetables.
Listeria is common in the environment and can originate from a variety of sources, including soil, water and animal digestive systems (which also means it can be found in animal feces).
Unlike many other bacteria, listeria can continue to grow in the cold, which means that when it’s in foods like ice cream, deli meats and cheese that spend a long time in the refrigerator, it has a longer time to reproduce in the food. The cold does nothing to stop it.
By the time these foods are eaten, the listeria bacteria have been given ample opportunity to grow, meaning the person eating the food will take in more bacteria.
Listeria also thrives in low-acidity, moist environments. Low-acidity foods that are often refrigerated for a long time, like melons, have been associated with listeria outbreaks in the past, as have foods that grow in humid conditions, like alfalfa sprouts.
Soft cheeses, like brie, Camembert and queso fresco, are known to be both moister and less acidic than hard cheeses, which makes them friendlier to listeria growth.
Dairy products made with unpasteurized milk are even more likely to be contaminated.
How does listeria get into cooked foods?
Deli meats are typically cooked when they’re produced, so how does listeria make its way into these foods?
Even though cooking the meat kills any listeria that may be present, deli meat can be contaminated afterward during packaging or slicing.
Similarly, the ready-to-eat meat products involved in the ongoing BrucePac recall are precooked, although the source of contamination hasn’t yet been determined.
Since listeria can come from many different sources, contamination can occur in a variety of ways. Prior outbreaks have been associated with the presence of listeria on floors, drains, tables, knives, conveyor belts and many other areas in processing facilities.
Once the processing equipment is contaminated, it becomes more difficult to sanitize because listeria has a tendency to form “biofilms,” in which the bacteria adhere more strongly to one another and to surfaces.
A listeria biofilm is more resistant to heat, acids, UV rays and other cleaning methods that would typically be used to kill the bacteria.
What are the dangers of listeria?
It can take anywhere from a few days to three months after eating contaminated food before symptoms start, but the typical time period is one to two weeks.
Almost one-sixth of all listeria cases occur in pregnant women, who are about 10 times more likely to experience an infection compared with the general population.
This makes it a serious concern for expectant mothers, since they and their babies can be affected. Listeria infection early in pregnancy can cause premature labor, a baby with a low birth weight and loss of the pregnancy. Later infection can lead to congenital health problems for the baby, including intellectual disability, seizures, blindness and more.
In some patients, the infection can cause death. According to the Centers for Disease Control and Prevention, around 1,600 people are infected and 260 people die from listeria infection in the United States every year.
It is the third leading cause of death from food poisoning.
Follow the ‘two-hour’ rule
Pregnant women, newborns, adults over age 65 and people with weakened immune systems should avoid commonly contaminated foods, like deli meats, unpasteurized dairy products and soft cheeses.
Studies have identified that pregnant Hispanic women may have a higher risk of listeria infection due to the consumption of queso fresco and other soft cheeses, so this group should take special care to avoid these foods when expecting.
It’s also important to keep your refrigerator clean to avoid the risk of listeria growth inside. That means cleaning up spills immediately and cleaning inside the walls and shelves with hot water and a mild dishwashing detergent.
Make sure not to eat foods that have passed their expiration dates.
Finally, the “two-hour rule” will help prevent the growth of listeria in prepared food and leftovers. Refrigerate or freeze food within two hours of preparation, and throw away food that has been out for longer.
