The Centers for Disease Control and Prevention is actively investigating a listeria outbreak that’s resulted in one death and sickened at least 16 people from New York to California. The ongoing outbreak is linked to deli meats and cheese.

“It's something we don't hear about often, but when we hear about it, it's usually a pretty serious foodborne illness breakout,” said Judy Simon, a dietician-nutritionist at University of Washington Medical Center.

Listeria, also known as listeriosis, is caused by eating food contaminated by bacteria that can spread from the gut to other parts of the body. Symptoms can include fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions, the CDC says.

Simon and the CDC say the following groups are at a higher risk for severe illness from a listeria infection:

• Pregnant people (can cause severe disease in the fetus or newborn baby)
• People ages 65 and older
• People with weakened immune systems 

In the current outbreak, deli meats and unpasteurized cheeses are two types of foods more likely to be linked to listeria. Simon encourages people at a higher risk of illness to heat these foods before eating them over the threshold in which listeria can live, which is 165 degrees Fahrenheit.

“The best idea is to use a food thermometer to make sure that it's at 165,” said Simon.

She also says individuals at a higher risk of a listeria-induced illness should quickly seek medical support if they think they might be infected.

“I think for that high-risk group, the bar should be pretty low. If you're pregnant and all of a sudden you're having diarrhea, something just doesn't feel right, I would get a hold of your healthcare provider,” Simon said.

Additional resources:

• Broadcast-ready soundbites with Judy Simon on listeria protection
• CDC listeria resource page