Gauteng accounts for 59% of reported cases, followed by Western Cape (12%) and KwaZulu-Natal (7%), the NICD said in a statement on Thursday.

The death toll represents the number of patients the NICD could follow up on, according to the head of the Centre for Enteric Diseases at the NICD, Dr Gina Thomas.

"These cases are not recent. Most of these cases are from mid- to late last year," she said.

Specialised tests were being conducted by experts at the NICD laboratories to assist in detecting the source as soon as possible.Thomas said that the health minister had put together a multi-sectoral team - which includes the Department of Agriculture, Forestry and Fisheries and the Department of Trade and Industry - to investigate.

"The Department of Agriculture, Forestry and Fisheries together with the Department of Health, is conducting a systemic sampling of the foods linked to listeriosis - from processed meat to dairy and produce," added Thomas.

The NICD said it remained optimistic that the source of this outbreak would be found, and urged members of the public not to panic unnecessarily.

"Members of the public are urged to be vigilant all the time by observing the above guidelines and to assist health authorities by spreading the message as widely as possible. Those in doubt must consult their nearest healthcare practitioners," the statement reads.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 6 hours to 70 days, poses a major challenge in determining the source of the outbreak.

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