South Africa Hit With Largest Ever Listeria Outbreak

South Africa has been struggling with a deadly listeria outbreak that has been hitting the country hard for over a year now.

Recently, the Minister of Health of South Africa, Dr. Aaron Motsoaledi, provided an update on the situation, reporting that as of March 2, 2018, the number of laboratory-confirmed cases of listeriosis has risen to 948 since January 2017—the cases are up by 221 since January 2018 alone. A total of 659 patients out of the 948 have been traced; 180 individuals have died. This equates to a 27% case fatality rate.

Since the outbreak began, health officials have been working doggedly to identify a potential source of the outbreak. In an effort to do this, officials from the National Institute for Communicable Diseases (NICD) interviewed 109 of the infected individuals to glean information pertaining to the foods that they consumed in the month prior to falling ill, according to Dr. Motsoaledi’s statement. They found that the majority of those interviewed (85%) consumed ready-to-eat processed meat products—polony, viennas/sausages, and other cold meats.

This, perhaps, is not surprising as many Listeria outbreaks that sprung up in the 1990s were linked primarily with deli meats and hot dogs. However, most recent outbreaks have been traced back to various dairy products and produce. For example, one of the most recent Listeria outbreaks was linked with soft raw milk cheese made by Vulto Creamery.

The outbreak occurring in South Africa is believed to be the largest-ever outbreak to have occurred to date, according to the United Nations. Previous to this, the second largest outbreak of listeriosis sprung up in 2011, and was linked with whole cantaloupes from Jensen Farms, Colorado—this outbreak had 147 confirmed cases across 28 states; 33 individuals died.

After 9 children under the age of 5 presented with febrile gastroenteritis at the Chris Hani Baragwanath Hospital, and the pediatrician suspected that they may be infected with a food-borne illness, environmental health practitioners (EHPs) were informed of the situation. On the same day that they were notified, the EHPs collected samples from 2 unrelated polony brands (Enterprise and Rainbow Chicken Limited), and then submitted the samples for laboratory testing. Upon further examination of a stool sample collected from 1 of the children, Listeria were identified. Whole genome sequencing found that 91% of the 9 sequence types of Listeria that were isolated were of sequence type 6 (ST6)—this outbreak is driven by ST6, according to Dr. Motsoaledi.

The next step of the investigation was to visit all food processing, packaging, and production sites. Following a lead, officials visited the Enterprise factory located in Polokwane, according to the statement, where they “conducted an extensive food product and environmental sampling.” Listeria was isolated in upwards of 30% of the environmental samples that officials collected. Whole genome sequencing found that at least 16 environmental samples collected from the site were of the outbreak strain.

“The conclusion from this is that the source of the present outbreak can be confirmed to be the Enterprise food-production facility in Polokwane,” Dr. Motsoaledi stressed.

Furthermore, officials have found that other ready-to-eat meat products from the Enterprise facility located in Germiston also contain Listeria, however, the sequence type is not yet known.

Meanwhile, officials are also investigation the RCL Wolwehoek production facility, where already, polony products have come back as positive for Listeria. However, the isolates are not ST6, he noted. Regardless, the contaminated food product still poses a public health risk. He added that upwards of 10% of environmental samples collected from the site were positive for Listeria as well.

In light of this information, Dr. Motsoaledi stressed that all consumers should avoid eating processed meat products that are sold as ready-to-eat. In addition, he underscored the importance of practicing the World Health Organization’s “5 Keys to Safer Food” program which calls for: keeping clean, separating raw and cooked food, cooking thoroughly, keeping food at safe temperatures, and using safe water and raw materials.

To keep track of the case counts associated with the Listeria outbreak in South Africa, be sure to visit our Outbreak Monitor.