Listeria is a kind of bacteria that can make you ill through food. It likes cold, ready-to-eat things that never get hot again — some soft cheeses, cold meat, leftovers sitting too long in the fridge. Many healthy people only get a mild fever or a bad stomach, or they feel nothing. Though actually, it is a much bigger worry for pregnant women, older people, and anyone whose body is already weak: it can reach the blood or the brain, and in pregnancy it can harm the baby. That is why you hear the word on the news when a shop recalls food, more than you hear it at the dinner table. Scientists write the group name Listeria with a capital L; everyday English often uses listeria with a small l. The illness has its own name, listeriosis.