Cause of listeriosis outbreak still unknown

The outbreak of listeriosis is continuing‚ with a total of 820 laboratory-confirmed cases recorded since January 2017‚ the National Institute of Communicable Diseases says.

Two weeks ago the institute said it had confirmed another 31 cases of listeriosis since January 3‚ which at the time brought the total number since the beginning of last year to 748.

This week‚ the institute said that most cases have been reported from Gauteng (59%) followed by Western Cape (13%) and KwaZulu-Natal (7%) provinces.

Cases have been diagnosed in both public (66%) and private (34%) healthcare sectors.

Ages range from birth to 93 years.

"At present‚ the source of the outbreak is not known‚" the institute said.

"Municipal Environmental Health Practitioners in all provinces have embarked on systematic inspection and sampling of meat and poultry production‚ processing‚ and packaging facilities.

"Cases of listeriosis will continue to be investigated‚ with trace back and further investigation of any positive food/environmental samples."

The number of fatalities is unclear. The institute says it has "outcome data" for 29% (238/820) of cases‚ of which 34% - 82 people - have died.

TimesLIVE reported earlier this month that the average mortality rate is between 20% and 25%.

Via genome sequencing‚ the NICD established that‚ in most cases‚ the listeria came from a single source‚ thought to be a particular product or range of products. Pretoria-based microbiologist and food safety expert Dr Lucia Anelich said the "culprit" was most likely a product eaten by consumers across the country and "extremely often".

Listeriosis symptoms develop any time between two and 30 days after eating food contaminated with the listeria pathogen. In pregnant women‚ they include mild‚ flu-like symptoms‚ headaches‚ muscle aches‚ fever‚ nausea and vomiting‚ and if the infection spreads to the nervous system it can cause a stiff neck‚ disorientation or convulsions.

High on the list of foods known to have caused other listeriosis outbreaks are ready-to-eat foods that consumers don’t cook or heat before eating‚ primarily deli meats - such as slices of ham‚ polony and cooked chicken.

"Deli meats are obviously consumed by a wide variety of people in the population‚ whether it’s a cheaper cut or a more expensive one‚" Anelich said. "But other products might also be just as implicated‚ and it’s really difficult to point a finger in a specific direction‚ considering we have absolutely no other leads at this stage."