IT has been more than a year since the first listeriosis case was reported to the National Institute of Communicable Diseases, however the source still remains unknown.

There have been 915 laboratory-confirmed cases of listeriosis and the outbreak has already claimed 172 lives.

Gauteng has the highest number of reported cases in South Africa with 59 per cent and KZN has reported seven per cent of the total cases.

Listeria is a bacterium that is naturally found in the environment. It commonly occurs in soil, water, vegetation and in the faeces of some animals.

It can contaminate a wide variety of food types, including meat and meat products, dairy products (unpasteurised and pasteurised), fresh and frozen produce (fruits, vegetables and sprouts) and ready-to-eat products. This fact, coupled with a variable incubation period that can range from six hours to 70 days, poses a major challenge in determining the source of the outbreak.