The number of cases reported since the official end of the 2017/2018 listeriosis outbreak is well within (and in fact, below) the expected range for sporadic disease. Furthermore, there have been no unusual trends in the epidemiological patterns of disease, or in the whole genome sequencing analysis of isolates from patients; such data are analysed on an ongoing basis in order to detect possible clusters or outbreaks.

Listeria monocytogenes is ubiquitous in the environment, so it is likely that accidental contamination of food occurs fairly frequently, and that consumption of contaminated food may lead to listeriosis particularly in vulnerable people at high risk for disease.

Worldwide, most listeriosis cases are sporadic (i.e. isolated cases that are not linked to an outbreak, occurring predominantly in persons at high risk for disease), but occasional outbreaks do occur.

The population incidence of sporadic listeriosis ranges from 2 to 5 cases per 1 million population in the US, Europe, and Australia, where listeriosis has been under routine surveillance for many years and robust data is available.

With that in mind, at our current population size of 58.8 million, we would expect 117 to 294 sporadic cases in South Africa per year. Data for South Africa from 2013 show that prior to the 2017/2018 listeriosis outbreak, 55 to 113 cases per year were reported (see Figure below).

For the 12 months following the official end of the 2017/2018 outbreak (3 September 2018 – 18 September 2019), a total of 87 laboratory-confirmed listeriosis were reported. This is below the expected range. Outcome data is currently available for 77% (67/87) of cases, of which 31% (21/67) died. This is not unexpected, because listeriosis is a severe disease that targets vulnerable people at high risk and typically has a fatality rate of 20-30%.

The National Department of Health together with the WHO convened a joint WHO-RSA listeriosis incident management team (IMT) made up of senior officials from the Departments of Health (including Environmental Health), Agriculture, Trade and Industry and Environment, and the NICD. The activities of the IMT to strengthen food safety, especially in ready-to-eat meat, include the following:

• Ongoing surveillance and investigation of human listeriosis cases by the NICD, to identify clusters of cases and detect outbreaks early;
• Inspection of all ready-to-eat processed meat facilities across the country. These inspections have been done together with the district municipalities and metros, and are ongoing;
• Review of molecular sequence data of environmental isolates, food and patient isolates to establish if links are present. To date, the NICD has not linked human cases to specific foods or environments other than the recent outbreak;
• Revised regulations pertaining to the application of the hazard analysis and critical control system (HACCP), (R908 of 2003) were published on 14 June 2018 in the Government Gazette as Notice R.607. This regulation requires all producers of ready-to-eat processed meat to be HACCP certified by an external agency by March 2019.

Cases of listeriosis have been documented in South Africa for many years, and sporadic cases will continue to occur. In keeping with international recommendations, persons at high risk for disease (including pregnant women, those with HIV, diabetes, cancer, liver or kidney disease, and those aged over 65 years) should preferably avoid foods that are at high risk of contamination with listeriosis. This includes dairy products (especially unpasteurised products and soft cheeses), read-to-eat processed meat, and raw fruit and vegetables.

To decrease the risk of listeriosis and other foodborne diseases, all persons are advised to practice food safety measures including

• Practice good hand hygiene – including washing hands before and after eating, and preparing food
• Separate raw and cooked food
• Cook food thoroughly
• Keep food at safe temperatures
• Use safe water and safe raw foodstuffs when preparing food.

Woolworths has announced a recall of their frozen savoury rice product as a precautionary measure; the product contains frozen corn and is reportedly sourced from Belgium. This follows on an alert issued by the Hungarian Food Safety Agency to the global food industry. On 29 June 2018, the Hungarian Food Chain Safety Office banned the marketing of all frozen vegetables and frozen mixed vegetables produced by the company between August 2016 and June 2018 and ordered their immediate withdrawal and recall. All freezing activity at the plant was stopped in June 2018.

The ECDC advises that to reduce the risk of L. monocytogenes infection due to frozen vegetables, consumers should thoroughly cook frozen vegetables that are not labelled as ready-to-eat, even those that are sometimes consumed without cooking, for example in salads and smoothies.

We encourage all persons at high risk for listeriosis to cook frozen vegetables before eating (cook thoroughly in boiling water or heat to high temperatures (≥70°C)).

People at high risk for listeriosis include:

∙             pregnant women

∙             very young infants

∙             persons >65 years of age, and

∙             anyone with a weakened immune system (due to HIV infection, cancer, diabetes, kidney disease, liver disease, people with transplants and those on immunosuppressive therapy such as oral corticosteroids, chemotherapy, or anti-TNF therapy for auto-immune disease).

Reference:

https://ecdc.europa.eu/sites/portal/files/documents/2018_ECDC-EFSA_ROA_Update1_UI-444_Listeria.pdf