At a glance
- People who eat food contaminated with Listeria bacteria can get a harmful infection.
- Soft cheeses, which are high in moisture, are more likely to be contaminated than hard cheeses.
- Outbreaks of Listeria infection have been linked to many kinds of soft cheeses, including queso fresco, feta, Camembert, and Brie.
- Raw (unpasteurized) milk and products made from it, including cheese, yogurt, and ice cream, also can be contaminated with Listeria.
Soft cheeses
Soft cheeses are more likely than hard cheeses to be contaminated with Listeria because of their high moisture, low salt content, and low acidity. These conditions support the growth of Listeria.
Soft cheeses made with raw (unpasteurized) milk or made in facilities with unclean conditions are even more likely to be contaminated. Pasteurization heats milk to a high enough temperature for a long enough time to kill germs. Although pasteurizing milk kills germs, cheese made with pasteurized milk can still get contaminated during cheese-making.
- Soft cheeses include queso fresco, queso blanco, queso panela, Brie, Camembert, and blue-veined.
- Hard cheeses include Asiago, Cheddar, Emmental, Gruyere, Parmesan, and Swiss.
Recent multistate outbreaks:
Raw (unpasteurized) milk and products made from it
Raw milk is milk that has not been pasteurized. Pasteurization heats milk to a high enough temperature for a long enough time to kill germs.
Raw milk and products made from raw milk, including cheese, ice cream, and yogurt, might contain Listeria and other harmful germs.
It's important to understand that raw milk can be a source of foodborne illness. While good practices on farms can reduce contamination, they cannot guarantee safety from harmful germs. Pasteurized milk offers the same nutritional benefits without the risks of raw milk consumption.
CDC recommends that everyone choose pasteurized milk and dairy products.
Multistate outbreak:
Show me the science
Soft cheeses
Jackson K, Gould L, Hunter JC, Kucerova Z, Jackson B. Listeriosis outbreaks associated with soft cheeses, United States, 1998–2014. Emerg Infect Dis. 2018;24(6):1116-1118. Listen to a CDC podcast about this study or read the podcast transcript [PDF – 3 pages].
Ibarra-Sánchez LA, Van Tassell ML, Miller MJ. Invited review: Hispanic-style cheeses and their association with Listeria monocytogenes. J Dairy Sci. 2017;100(4):2421-2432.
Gould LH, Mungai E, Behravesh CB. Outbreaks attributed to cheese: differences between outbreaks caused by unpasteurized and pasteurized dairy products, United States, 1998-2011. Foodborne Pathog Dis. 2014;11(7):545-51.
Raw milk and milk products
Committee on Infectious Diseases, Committee on Nutrition. Consumption of raw or unpasteurized milk and milk products by pregnant women and children. 2014;133(1):175-9.
See more scientific papers on the Listeria publications page.