A Prolonged Outbreak of Enteric Fever Associated With Illegal Miners in the City of Matlosana, South Africa, November 2020-September 2022

Abstract

Background: In South Africa, the annual incidence of enteric fever averaged 0.1 per 100 000 persons between 2003 and 2018. During 2021 an increase in the number of enteric fever cases was observed. An outbreak investigation was conducted to determine the magnitude and source of the outbreak.

Methods: We performed a cross-sectional descriptive study. Data were collected through telephonic or face-to-face interviews with cases or proxies via a standardized case investigation form. Whole genome sequencing was performed on all Salmonella Typhi isolates. Drinking water samples were collected, tested, and analyzed. Descriptive analysis was performed with Microsoft Excel.

Results: Between January 2020 and September 2022, a cluster of 53 genetically highly related Salmonella Typhi isolates was identified from 5 provinces in South Africa. Isolates associated with the cluster showed ≤5 allelic differences, as determined following core genome multilocus sequence typing analysis. Most cases (60%, 32/53) were in the North West province. Males represented 68% (36/53). Of these, 72% (26/36) were aged 15 to 49 years, with a median age of 31 years. Where occupation was known within this age group, 78% (14/18) were illegal gold miners. Illegal miners reported illness onset while working underground. Five municipal tap water samples were tested and showed no evidence of fecal contamination.

Conclusions: This outbreak predominantly affected illegal gold miners, likely due to the consumption of contaminated groundwater while working in a gold mine shaft. In addition, this investigation highlights the value of whole genome sequencing to detect clusters and support epidemiologic investigation of enteric fever outbreaks.

Keywords: carrier; enteric fever; illegal miner; prolonged outbreak.

Figure 1.

Cases of laboratory-confirmed enteric fever, South Africa, 1 January 2003–22 September 2022.

Figure 2.

Annual proportions of laboratory-confirmed cases of enteric fever by province, South Africa, 1 January 2003–22 September 2022.

Figure 3.

Distribution of laboratory-confirmed outbreak cases of enteric fever by sex and age, South Africa, 1 January 2003–22 September 2022 (N = 53).

Figure 4.

Epidemic curve of laboratory-confirmed outbreak cases of enteric fever by occupation, South Africa, 1 January 2003–22 September 2022 (N = 53).

Figure 5.

Minimum spanning tree drawn according to cgMLST data from Salmonella Typhi isolates sourced from South Africa, 2020–2022. The circular nodes represent isolates. Isolates showing ≤5 allelic differences are collapsed into a single circular node. cgMLST, core genome multilocus sequence typing.