Listeria causes listeriosis, a rare but potentially life-threatening disease.
Healthy adults are likely to experience only mild infection, causing flu-like symptoms or gastroenteritis. However, listeriosis is dangerous to pregnant women, the elderly and people with weakened immune systems.
Listeria is typically spread by contaminated foods. Listeria is an unusual bacterium because it can grow at low temperatures, including refrigeration temperatures of below 5°C. It is, however, killed by cooking food thoroughly and by pasteurisation.
Some listeriosis cases occur through contact with animals. Pregnant women are especially at risk and should avoid close contact with sheep who are giving birth, to protect themselves and their unborn child.