Since the beginning of 2017, South Africa has been experiencing a listeriosis outbreak. Between 1 January 2017 through 14 March 2018, 978 laboratory-confirmed listeriosis cases have been reported to the National Institute for Communicable Diseases (NICD) from all provinces.

Listeria bacteria
Listeria monocytogenes/CDC

The majority of cases have come from three provinces: 581 (59%) from Gauteng, 118 (12%) from Western Cape and 70 (7%) from KwaZulu-Natal provinces, with the remaining cases coming from the other provinces in South Africa.

183 fatalities have been reported, or a 27 percent Case-fatality rate, a number comparable to other recorded listeriosis outbreaks worldwide.

Most of the cases are persons who have higher risks for a severe disease outcome, such as neonates, pregnant women, the elderly and immunocompromised persons. In this outbreak, 42% of the cases are neonates who were infected during pregnancy or delivery.

Whole genome sequencing was performed on isolates from a large subset of patients. Ninety one percent of the strains belonged to Listeria monocytogenes Sequence Type 6 (ST6). The same ST6 sequence type was identified in a widely consumed ready-to-eat processed meat product called “Polony”. The same strain was also found in the processing environment of the manufacturer of the implicated product.

The food processing company and three of its retailers export to 15 countries in the African region . All of these countries have issued recalls for the implicated products.

Nine percent of the reported cases in the present outbreak in South Africa were infected with different strains of Listeria than the predominant ST6 outbreak strain. This may indicate that more than one outbreak is ongoing.