What is listeria, the bacteria suspected of causing two deaths after eating contaminated cheese?

Listeria, suspected of causing the deaths of two people in France after consuming contaminated cheese produced by the same cheese factory, is one of the leading causes of fatal food poisoning.

Health authorities have identified 21 cases of listeriosis, including the two deaths, which could be "possibly linked" to the consumption of pasteurized milk cheeses from the Chavegrand cheese factory, which were the subject of a rare recall.

Listeria monocytogenes infection is the second leading cause of death from food poisoning, with a few dozen deaths per year in France. Only salmonella , also a bacteria, causes more fatal cases of poisoning: several hundred each year. In its so-called "invasive" form, listeriosis is particularly deadly: around a quarter of patients die from it, for example, due to neurological complications such as meningitis.

The incubation period generally lasts one or two weeks, but can last up to eight weeks (or even more than three months), and pregnant women are particularly at risk, with a twenty times greater risk of developing this infection than the rest of the population.

Like salmonellosis, listeriosis is treated with antibiotics. This distinguishes it from another family of bacteria that is a hallmark of foodborne illnesses, E. coli. The latter—in their dangerous forms, many of which are harmless—cause fewer serious illnesses than listeria and salmonella, but they are more difficult to treat because antibiotics are ineffective.

Another common point between salmonella and listeria is that they are eliminated by cooking and are therefore found in raw or undercooked foods: meat, dairy products, fresh vegetables and fruits... But listeria also has its specificities. While cold slows the development of salmonella, this is not the case for listeria, which can reproduce in large numbers in a refrigerator. Listeriosis is therefore often linked to "foods that can be stored for a long time in refrigerated conditions," summarizes the World Health Organization.

Also read

Selection “Food poisoning: threats on our plates”, nightmares in the kitchen