Listeriosis: what you need to know

As the department of health hunts for the source of the listeriosis disease, more information on this deadly bug is needed.

With 61 people dead, 40% of who were neonatal babies, The Citizen reached out to international food safety expert Dr Lucia Anelich, the only South African member of the International Commission on the Microbiological Specifications for Food, current president of the SA Association for Food Science and Technology, and chairperson of the SA Bureau of Standards food hygiene committee.

“Listeria was not a known problem for humans before the early ’80s, and was more commonly known to cause disease in animals,” Anelich said.

“But bacteria and viruses change or simply switch host and this can be due to environmental pressure,” she said, claiming this was the worst documented listeriosis outbreak in global history.

“The organism is found in soil, water, sewage and decaying vegetation.

“Because bacteria and viruses are biological entities, they can mutate or pick up genes from other micro-organisms in their environment.”

This can lead to either the creation of a complete new micro-organism or a different strain.

The last massive listeriosis outbreak in 2011 in the US, which killed 30 people and infected 147, was finally traced to cantaloupes.

According to Anelich, listeria monocytogenes could cause a mild, non-invasive illness called listerial gastroenteritis, which showed typical symptoms of a tummy bug with fever and diarrhoea.

“This form of the illness usually passes quickly without severe effects.”

The other side of the coin was the severe, invasive illness responsible for infecting 727 people so far.

“Listeriosis is characterised by a relatively high mortality rate of between 20% to 25%, compared to most other foodborne pathogens such as Salmonella (less than 1%) or E. coli O157.

“In the invasive form of the illness, the organism has moved beyond the gut and has infected other parts of the body,” Anelich said.

Foods most often implicated in foodborne outbreaks globally include ready-to-eat deli meats (polonies, ham products, hot dogs, refrigerated pâtés or meat spreads), unpasteurised milk and dairy products, soft cheese made with unpasteurised milk, such as queso fresco, Feta, Brie, Camembert, as well as refrigerated smoked seafood, raw sprouts, prepackaged salads, and ice cream – the latter not as common said Anelich.

“Pregnant women are approximately 20 times more likely than other healthy adults to get listeriosis.

“They typically experience only fever and other flu-like symptoms, such as fatigue and muscle aches.

“However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the new-born, such as meningitis,” Anelich said.

In the invasive form of the illness, the organism has moved beyond the gut and has infected other parts of the body.