Listeria grows at fridge temperatures, so it specializes in chilled, ready-to-eat foods: soft cheese, deli meats, smoked fish, pre-packaged sandwiches.
The CDC describes two illnesses: an intestinal version with diarrhea and vomiting, and an invasive version with fever, muscle aches, stiff neck, confusion, and worse. It especially harms pregnant women, newborns, over-65s, and the immunocompromised, and in pregnancy it can cause miscarriage or stillbirth per the NHS. Prevention: cold fridge, strict use-by dates, steaming-hot reheating, and avoiding high-risk foods when vulnerable. Fever after a risky food in a high-risk person needs a doctor, since antibiotics treat it when caught.
What to do
Common questions
What is listeria?
Listeria is a bacterium with one unusual talent: it grows at refrigerator temperatures, so chilled ready-to-eat foods are its home turf, which is why the risky foods are things like soft cheeses, cold deli meats, smoked fish, and pre-packaged sandwiches and salads. The CDC says listeria can cause two kinds of illness: an intestinal one, days of diarrhea and vomiting, and an invasive one, where it spreads beyond the gut to cause fever, muscle aches, headache, stiff neck, confusion, loss of balance, and seizures. Who actually needs to worry: the CDC names pregnant women, newborns, adults 65 and older, and people with weakened immune systems as those it can especially harm, and notes other people rarely become seriously ill. In pregnancy the stakes are specific: the NHS says listeriosis can cause miscarriage or stillbirth or make a newborn very unwell, which is why the pregnancy food rules exist. Prevention is temperature and timing: keep the fridge at 5°C or below, respect use-by dates on ready-to-eat foods, heat deli meats and ready meals until steaming, and avoid the classic high-risk list in pregnancy and when immunocompromised. Fever or flu-like symptoms after a high-risk food, in a high-risk person, is a call-the-doctor situation because listeriosis responds to antibiotics when caught.