Four years after the NICD linked Tiger Brands’ polony to the Listeria Outbreak

By Bill Marler on 27 May 2022

We are now beyond four years from the date that the NICD announced the association between Tiger Brands’ polony products and the outbreak, and the work done by all parties has only generated more evidence that the NICD’s and Tiger Brands’ conclusions are accurate. There is no evidence to the contrary.

In 2017 and 2018, the world’s largest and deadliest outbreak of listeriosis occurred in multiple provinces of South Africa (Figure 1). The outbreak was caused by contaminated polony, a ready-to-eat, processed meat product. Ready-to-eat, processed meats are a well-known vehicle for listeriosis outbreaks (Thomas et al., 2020). The Minister of Health declared that there was an outbreak of listeriosis on December 5, 2017, and, on March 4, 2018, further identified Tiger Brands’ polony products as the cause of the outbreak. The Minister of Health instructed Tiger Brands to recall all polony products the same day. See generally, Minister of Health September 3, 2018, Media Statement. The Ministry of Health based its conclusions on the investigative findings of the Joint Public Health Emergency Coordinating Committee, which was established for the specific purpose of identifying the cause of the outbreak and developing measures to prevent further illnesses and other outbreaks associated with processed meat products generally. Id. The relevant epidemiologic findings are set forth in the paragraphs that follow.


Figure 1. Incidence of Laboratory-Confirmed Listeriosis Cases during the Outbreak Period, According to South African Districts (Thomas et al., 2020).

Cases were reported from across the country, with most cases reported from Gauteng Province (58%). Women accounted for 55% of total cases. The ages of cases ranged from birth to 93 years. Neonates (aged £ 28 days) were the most affected age group, accounting for 43% of cases. This was followed by adults of 15 to 49 years of age, accounting for 32% of cases. The disease outcome was known for 806/1,060 (76%) of cases; 27% (216/806) had the known outcome “died” (Smith et al., 2019).

Listeriosis is a serious foodborne infection with a case-fatality rate (“death rate”) of 20-30% (Thomas et al., 2020). People primarily affected by listeriosis have impaired cell-mediated immunity. This includes those who are pregnant, elderly, or immunocompromised from conditions such as HIV, chronic disease, or immunosuppressive therapy (Thomas et al., 2020). The specific outbreak strain associated with the outbreak was Lm ST6. There are two ways that listeriosis can manifest: febrile gastroenteritis and invasive listeriosis (Coulombier). Invasive listeriosis is characterized by bacteraemia, meningitis, pneumonia, endocarditis, and sepsis (Smith et al., 2019).

A total of 1,060 cases were reported during the period of January 11, 2017, to July 17, 2018 (Figure 2) [1]. The outbreak period was defined as a duration of time during which case numbers exceeded and remained above a weekly threshold of five cases per epidemiological week (Thomas et al., 2020). At the peak of the outbreak (mid-November 2017), 41 listeriosis cases were reported in a single week. Prior to this outbreak, listeriosis was not a reportable disease in South Africa; therefore, information is not available on the prevalence, epidemiology, and description of clusters/outbreaks on listeriosis. Due to the lack of surveillance data, the baseline number of listeriosis cases was estimated from counts of listeriosis cases in 2016.

It is known that in 2015 and 2016, clusters of listeriosis occurred in South Africa. The 2015 listeriosis cluster involved 7 cases total, and the predominant strain was Lm ST6. However, researchers did not have sufficient epidemiologic evidence to connect the 2015 cluster to any specific food product (Shuping et al., 2015). For the 2016 cluster, retrospective analysis of Lm cases from the years 2012-2016 was used to calculate the expected case numbers for years 2013, 2014, 2015, and 2016 in the Gauteng province (Mathebula et al., 2016) [2]. Because there were only 3 cases in the 2016 cluster, researchers needed to estimate the baseline number of cases.

When determining if a cluster of diseases is classified as an outbreak or epidemic, it is essential to know what the baseline number of illnesses is in the population of interest. An epidemic refers to an increase in the number of cases of a disease, above what is normally expected in that population in that area, and an outbreak is defined the same but is often used for a more limited geographic area (Centers for Disease Control and Prevention [CDC], 2012).


Figure 2. Distribution of Laboratory-Confirmed Cases of Listeriosis, According to Outbreak Week and Major Events (January 1, 2017 to August 21, 2018) (Thomas et al., 2020).

Case definitions are used in outbreak investigations to help identify cases that are associated with the outbreak. A case definition includes criteria such as the subject population, implicated location, time, clinical features, and/or laboratory test results if available (CDC, 2012). The initial case definition for the primary listeriosis outbreak included all cases of listeriosis that occurred in South Africa from 2017 to 2018. The initial case definition was appropriate due to the lack of whole-genome sequencing (WGS) data at the beginning of the investigation. Multilocus sequencing typing (MLST) was used later to analyse the WGS results from all viable isolates obtained from case patients. Researchers discovered that 93% of the clinical isolates collected from cases during the outbreak period were Lm ST6 (Thomas et al., 2020; Gerner-Smidt). The case definition later included sequence typing information to increase the likelihood of identifying a common source (Besser). This finding also showed that the outbreak strain of Listeriosis was definitively the Lm ST6 strain.

Further, we note that investigators thoroughly analysed the theoretical possibility that Lm ST6 was coming from more than just Tiger Brands’ polony products. In short, after conducting environmental investigations at all 157 ready-to-eat meat production facilities in South Africa, there was no Lm ST6 in any other products or facilities except Tiger Brands.

Together with the NCID’s clear statements that Tiger Brands polony products were the source of the outbreak, based on epidemiologic and environmental evidence, the constellation of all evidence conclusively establishes that Tiger Brands’ polony products were in fact the sole source. There is no additional analysis that will materially change these facts.

Based on its investigation findings, the Minister of Health issued a recall of Tiger Brand’s ready-to-eat meat products produced at the Enterprise facility. The Minister of Health also recalled all ready-to-eat meat products produced at Rainbow Foods, but epidemiologic and environmental findings during the investigation showed that this was a precautionary measure only—i.e., the Listeria identified at the Rainbow Foods’ production facility on environmental testing was not Lm ST6, and therefore had no causal association with illness in the outbreak. See Minister of Health March 4, 2017 Statement. Shortly after Tiger Brands’ recall, the outbreak essentially stopped (Figure 3).


Figure 3. Epidemic curve of laboratory-confirmed listeriosis cases by date of clinical specimen collection (n=1 038) and sequence type (ST) (n=564), South Africa, 01 January 2017 to 5 June 2018 (n=1049)

The environmental and epidemiologic investigative findings establish the likely causal nexus between Tiger Brands’ polony products and most all Listeriosis cases that occurred in South Africa before, during, and after the outbreak period. (Coulombier).  As stated above, 93% of clinical isolates that underwent sequencing were shown to be Lm ST6, the strain that was both epidemiologically associated with illness and repeatedly found in the production environment at the Enterprise facility, and nowhere else. But not all isolates could be sequenced, due to the lack of laboratory resources and personnel available (Besser). Based on the high percentage of Lm ST6 clinical isolates, it is highly likely that a similar percentage of non-sequenced isolates would have been Lm ST6 if sequencing could have been done (Coulombier). As further support that there was no difference between the distribution of sequence types among the non-sequenced samples and the distribution of sequence types observed in the sequenced samples, the process of selecting case isolates to be sequenced was not biased. Therefore, it is a statistically valid and provable fact that, in the absence of evidence to the contrary—i.e., sequencing that showed that a clinical isolate was not Lm ST6–a listeriosis patient diagnosed during the outbreak period had a > 90% probability of being related to the outbreak even without confirmed laboratory results (Gerner-Smidt).

After detecting the outbreak, the Centre for Enteric Diseases, a part of the National Institute for Communicable Diseases, conducted a nested case-control study that provided evidence that cases with Lm ST6 infections were more likely to have eaten polony than those with non- Lm ST6 infections (Thomas et. al, 2020). In outbreak investigations, case-control analysis is performed to estimate the odds ratio for the association between specific food items and the outbreak-associated illness. For this nested case-control study, case patients were those with Lm ST6 infections, and control patients were people infected by another strain of LM (i.e., not Lm ST6) during the outbreak period. Results from this study show that the odds ratio was 8.55 with a 95% confidence interval of 1.66 – 43.35. An odds ratio is a measure of association between the odds of becoming ill from consuming a specific food item versus the odds of becoming ill without having consumed the specific food item (Coulombier). An odds ratio of 8.55 signifies that the odds of having eaten polony in Lm ST6 cases is 8.55 times greater than the odds of having eaten polony in non-Lm ST6 cases. Based on the calculated confidence interval, this result is statistically significant because the confidence interval does not include the null value of 1. Therefore, 95% of the time, the true odds ratio fell within this interval.

Prior to the study, food history interviews were conducted to generate a hypothesis as to which food item could have been the source of the outbreak (Coulombier). The food histories were conducted with the use of a standardized questionnaire that inquired as to food consumed by a case patient over the four weeks prior to onset of symptoms. Open-ended questions were posed to Listeriosis cases to understand each case’s food habits, such as where they purchase food, name of restaurants patronized, and use (and name) of informal food vendors. Closed-ended questions were posed to determine each case’s exposure to specific food items associated with outbreaks in the past and locally consumed foods thought to pose a high risk for listeriosis such as processed meats (e.g., biltong), cold meats (e.g., ham, polony), soft cheeses, raw milk, and raw vegetables. Brand preferences were also captured in the form.  The combination of open and closed-ended questions was and continues to be standard practice for the conduct of epidemiologic investigations internationally and provided investigators with high-value data for consideration alongside other epidemiologic and environmental information.

The food history interviews were completed by November 1, 2017. The epidemiologic methods utilized throughout this investigation, including the case control, were robust and mirrored those used in high-level investigations throughout the world. The investigators’ multi-disciplinary investigative methods were fully appropriate for the outbreak circumstances (Besser).

On January 13, 2018, febrile gastroenteritis developed in 10 children from a nursery in Gauteng Province. Several stool samples were collected from the children, and one yielded Lm ST6. Sandwiches prepared and eaten at the nursery were the only common food exposure, and polony was the common ingredient. Polony was recovered from the nursery refrigerator, and Lm ST6 was identified in the polony produced at Tiger Brands Enterprise Facility in Polokwane (Thomas et al., 2020).

On February 2, 2018, an environmental investigation took place at the Tiger Brands Enterprise Facility in Polokwane following the discovery at the nursery (Gerner-Smidt). Of 317 environmental samples taken from the Polokwane facility, 47 tested positive for Listeria monocytogenes, and of the 47 that tested positive, 34 were subtyped as the outbreak Lm ST6 strain. Additionally, two of 13 samples of unopened polony loaves collected at the facility tested positive for Listeria monocytogenes, and both were subtyped as the outbreak Lm ST6 strain.

These facts stand in stark contrast to the investigations at all other South African ready-to-eat meat producers, during which investigations no Lm ST6 was recovered in any food or environmental sample.

The fact that the public health investigation involved environmental inspections and sampling at the production facilities of other ready-to-eat meat producers is remarkable. Indeed, the public health investigation of this outbreak was unprecedented in scope, even internationally, as it is, in our experience, unprecedented to engage in such robust investigation of producers whose products are not epidemiologically associated with an outbreak. Thus, the only epidemiologic evidence establishes that Tiger Brands, and Tiger Brands alone, produced product contaminated by Lm ST6 during the outbreak period. By incorporating findings from the epidemiologic, environmental, microbiologic, and traceback data, investigators provided conclusive evidence that the source of the outbreak was polony produced from Tiger Brands Enterprise Foods Polokwane production facility, and that there were no other possible causes.

Further, and as set forth previously, the Minister of Health identified Tiger Brands’ polony products as the source of the outbreak on March 4, 2018, and instructed Tiger Brands to recall all its ready-to-eat meat products. At the point in time that Tiger Brands’ polony products were taken off of store shelves and were no longer widely available for purchase and consumption in South Africa, the outbreak ended and listeriosis cases in South Africa shortly returned to their pre-outbreak baseline. As Figure 3 demonstrates, by mid-April 2018 (6 weeks after recall), fewer than 5 cases were reported weekly. Regarding those individuals who became ill between the date of Tiger Brands’ recall and mid-April 2018, listeriosis cases continued to become ill by consumption of Tiger Brands’ polony products that were purchased before the date of the recall, which was to be expected given the lengthy incubation period for listeriosis generally (from 3 days to over one month), or from Tiger Brands’ polony products that were simply not removed from store shelves in time.

Following the findings by the NICD, Tiger Brands conducted its own internal investigation into the outbreak. During this internal investigation, based on information set forth in the discovery conducted to date and Tiger Brands’ various public statements, Tiger Brands confirmed the presence of the Lm ST6 outbreak strain in both its products and various locations in the production environment at the Enterprise facility. Tiger Brands issued several public statements to this effect.

In a SENS statement dated 19 March 2018, Tiger Brands issued the following public statement:

“On 15 March 2018, Tiger Brands received confirmation from independent laboratory tests corroborating the DoH’s findings of the presence of LST6 in the environment at its Polokwane Enterprise Foods manufacturing Facility. In addition, there was a positive detection of LST6 on the outer casing of two samples.”

On 26 March 2018, Tiger Brands issued a public statement on its website reiterating the independent laboratory results announced in the SENS statement of 19 March 2018 as aforementioned which confirmed the presence Lm ST6 in the Tiger Brands Polokwane Facility. In the 26 March press statement, Tiger Brands CEO, Mr Lawrence Mac Dougall commented on this discovery and, inter alia, stated as follows:

“We are investing all our time and energy into not only understanding the cause of the LST6 detection, but also how it could have come into our facility.”

In a statement to shareholders dated 23 May 2018, Mr Mac Dougall stated that:

“The detection of the presence of Listeria ST6 in our factory in Polokwane was disappointing to us given our compliance with best practices and prevailing standards.”

In a SENS statement dated 25 April 2018, Tiger Brands reported that it had received independent laboratory test results following its own internal investigation which confirmed the presence of the Lm ST6 in samples of ready-to-eat meat products manufactured at the Polokwane Facility:

“The purpose of this announcement is to update shareholders on the results of the independent laboratory re-testing which was carried out in respect of the presence of LST6 in the above samples which were manufactured at the Enterprise Polokwane processing facility. On 24 April 2018, Tiger Brands received confirmation of the presence of LST6 in these samples.”

From both the NICD’s and Tiger Brands’ investigations into the outbreak, there is no evidence that the outbreak had any source other than Tiger Brands’ polony products. There is no epidemiologic support for that proposition, and there is no environmental support for that proposition because NICD found no other positive Lm ST6 samples at any other facility that produces ready-to-eat meat. In fact, Tiger Brands has, in unequivocal terms, admitted to this responsibility. For example, in the request Further Trial Particular, Tiger Brands affirmed its responsibility for Lm ST6 cases:

“Tiger Brands statement of 24 April 2018 was correct. Tiger Brands learnt that laboratory tests had found ST6 in ready-to-eat meat products from its Enterprise Foods manufacturing facility in Polokwane. It accepts that the laboratory findings were correct.”

“Tiger Brands does not know to what products the contamination extended or over what period it occurred. It accepts, however, that ST6 contaminated products from its Polokwane facility probably infected some of the people who suffered from listeriosis during the outbreak.”

“The defendants accept the test results that L. monocytogenes was detected in the polony water coolers at the Polokwane facility.”

Further, and following the Supreme Court of Appeal’s ruling in the third-party subpoena’s litigation, Tiger Brands issued the following statement to the press:

“On Friday, 4 February 2022, the Supreme Court of Appeal overturned the earlier order of the Gauteng Division of the High Court, Johannesburg which required various third parties to hand over epidemiological information relating to the listeriosis outbreak.”

“The 2018 listeriosis outbreak affected many South Africans. We are saddened by the impact it has had on the lives of the victims and those who have lost loved ones from the outbreak. Tiger Brands reiterates its commitment to ensure that a resolution of the matter is reached in the shortest possible time, in the interest of all parties, particularly the victims of listeriosis.”

That Tiger Brands is liable for the manufacture and sale of contaminated polony products that injured people is beyond doubt; the scientific findings from the multi-disciplinary investigation allow only this conclusion, and the functional life of the outbreak ended when Tiger Brands was ordered to withdraw its products from the market. The epidemiologic implications of NICD’s sequencing effort are conclusive, which is the preliminary point made by SAAFOsT, in which organization Tiger Brands is a custodian member, in its December 2017 statement that:

“This is undoubtedly one of the worst listeriosis cases in global history. A large percentage (74%) of all the clinical isolates belong to the same sequence type i.e. ST6—this means that these isolates originate from a single source, most likely a food product on the market.”

What SAAFOsT did not have the benefit of then knowing, however, was that sampling at Tiger Brands’ Polokwane facility would validate in every respect the epidemiologic implications from NICD’s sequencing efforts on human isolates.

We are now beyond four years from the date that the NICD announced the association between Tiger Brands’ polony products and the outbreak, and the work done by all parties has only generated more evidence that the NICD’s and Tiger Brands’ conclusions are accurate. There is no evidence to the contrary.


[1]  Note: 23 October 2016 to 3 September 2018 is the “Outbreak Period” in the Certification Order.

[2] The oldest South African CT4148 isolates date from September 2015 and are related to a cluster of three cases of listeriosis in Western Cape Province28; this finding suggests a potential epidemiologic link to the 2017–2018 outbreak. Thomas, et al., 2020


Besser, J. (2020). Expert Opinion Regarding a Listeria Outbreak in South Africa Involving Tiger Brands Limited.

Coulombier, D. (2020). Expert Opinion Regarding a Listeria Outbreak in South Africa Involving Tiger Brands Limited.

Gerner-Smidt, P. (2020). Expert Opinion on Subtyping Aspects of the Listeria Outbreak in South Africa Involving Tiger Brands Limited.

Smith, A. M., et al. (2019). Outbreak of Listeria monocytogenes in South Africa, 2017-2018: Laboratory Activities and Experiences Associated with Whole-Genome Sequencing Analysis of Isolates. Foodborne Pathog. Dis. 16(7): 524-530. doi:10.1089/fpd.2018.2586

Thomas, J., et al. (2020). Outbreak of Listeriosis in South Africa Associated with Processed Meat. N. Engl. J. Med. 382: 632-643. doi:10.1056/NEJMoa1907462

Tiger Brands SENS statement dated 19 March 2018, “Financial Impact of Product Recall and Suspension of Operations at the Polokwane, Germiston, Pretoria and Clayville Processing facilities of Value-Added Meat Products (“VAMP”); Institution of Class Action; and Results of Independent Tests carried out in respect of the presence of Listeria monocytogenes ST6 type (“LST6”)”

Tiger Brands Public Statement dated 26 March 2018, “Tiger Brands Listeria Update”

Tiger Brands SENS Statement dated 23 May 2018, “Unaudited group results and dividend declaration for the six months ended 31 March 2018.

Tiger Brands SENS Statement dated 25 April 2018, ‘Results of Independent Tests carried out in respect of the presence of Lister monocytogenes ST6 type (“LST6”)’

Tiger Brands response to Plaintiff’s Further Particulars

Rose, “Tiger Brands Tall Tale”. Financial Mail, 10 February 2022.

Shuping, L., et al. (2015). Investigating a cluster of Listeria monocytogenes cases in the Western Cape province of South Africa, September 2015.

NICD. (2016). Investigation of Listeria monocytogenes cases at Charlotte Maxeke Johannesburg Academic Hospital in Johannesburg, December 2016.

NICD, Listeriosis Outbreak Situation Report. Dated 11 June 2018.

SAAFOST, “Listeriosis Outbreak in South Africa – Latest! By Dr Lucia Anelich, SAAFoST President”. Dated 20 December 2017.

Read the original article here, from Marler Clark

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