The infection is caused by the germ Listeria monocytogenes and people usually become ill around one to four weeks after eating contaminated foods. Foods that are most likely to be contaminated include soft cheeses made with unpasteurised milk, certain ready-to-eat meats, refrigerated smoked seafood, melons and raw dairy products.
Those at greatest risk of becoming seriously ill from the disease are pregnant women and their new-borns, older adults, and people with weakened immune systems. It is fatal for one in five people with the infection.
Symptoms include headaches, stiff neck, confusion, loss of balance, seizures, fever and muscle aches. Pregnant women tend to experience only fever and other flu-like symptoms, but infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the new-born.
The current situation in South Africa is an ongoing outbreak that began in January 2017, with around 1,000 people having become ill since this time. Most illnesses have been reported in Gauteng, Western Cape, and KwaZulu-Natal provinces, but illnesses have occurred throughout the country. More than 180 people have died from the infection.
The source of the outbreak has been identified in a variety of processed, ready-to-eat meat products, including ‘polony’, aka bologna sausage.