FEATURE | Posted April 24, 2015

What is listeria?

What you and your family need to know

Photograph of listeria © iStockphoto
Listeria monocytogenes is a bacterium that can contaminate food.

With the recent outbreak of listeria from certain Blue Bell brand ice cream products and possible contamination in Sabra hummus, the average consumer might be wondering what exactly listeria is, who is at risk and how to prevent a listeria infection.

Dean Blumberg, chief of pediatric infectious diseases at UC Davis Children’s Hospital, answers those questions and more.

What is listeria?

Listeria monocytogenes is a bacterium that can contaminate food. It’s a pretty hearty bacteria that can live a long time in the environment and a long time in food.

What types of food are prone to listeria?

It can be found in:

  • Dairy products, including unpasteurized milk
  • Soft cheeses, like queso fresco
  • Deli items, including cold cuts and hot dogs
  • Fruits and vegetables

Who is most at risk for becoming ill with listeria?

Everybody can be at risk for getting infected. The following groups are at higher risk for symptoms and have more severe manifestations of the disease:

  • Women who are pregnant
  • Newborns
  • Anyone over 50 years of age
  • Those with a compromised immune system

Symptoms can show up anytime between one day and three weeks after exposure. The symptoms can be flu-like, including fever and malaise, and gastrointestinal, usually diarrhea. It can be more invasive for the previously mentioned risk groups, and can lead to septicemia and meningitis.

How common is listeria?

There are about 1,500-2,500 cases in the United States each year, and about 500 deaths. At UC Davis Children’s Hospital, we see about one newborn case a year.

What should someone with symptoms do?

If someone is symptomatic and had the recalled hummus or ice cream, I’d recommend seeing your health care provider and I would make sure to mention that to them. If you have any of the recalled products in your home, throw them away. If animals can get into the garbage, wrap them in a plastic bag and then throw them away.

How can people avoid getting listeria?

Follow safe food handling and cooking recommendations:

  • Wash fruits and vegetables thoroughly.
  • Make sure any cooked foods are cooked appropriately, to 165 degrees Fahrenheit.
  • When reheating leftovers, make sure they’re completely reheated.
  • Thoroughly clean all utensils and preparation surfaces.
  • Be aware of any recalls by visiting http://www.recalls.gov/food.html.
  • If you are in a risk category, you may want to avoid some of the higher risk items.

The safe food handling recommendations are not just applicable for listeria. E. coli can be found in different foods, like ground beef, but the same precautions apply.