Epidemiological investigation of a typhoid fever outbreak in Sekhukhune District, Limpopo province, South Africa - 2017

BACKGROUND

Typhoid fever remains a public health concern in South Africa, where the risk of transmission is high because of poor access to safe water and sanitation. This study describes the investigation of typhoid fever outbreak in Limpopo province.

METHODOLOGY

Following notification of laboratory-confirmed cases, a descriptive study was conducted at Sekhukhune District, Limpopo province. A suspected case was defined as any person residing in Makhuduthamaga Municipality from November 2017 to January 2018, presenting with fever and gastrointestinal symptoms. Data were collected using case investigation forms. Whole-genome sequencing (WGS) was carried out on Salmonella Typhi isolates and polymerase chain reaction (PCR) test was done for Salmonella species from water samples. Location of cases and water sources were mapped using ArcGIS mapping tool.

RESULTS

Amongst 122 cases, 54% (n = 66) were female and 6% (n = 7) laboratory-confirmed. The median age of the cases was 11 years (range 2-83 years), with 79% (n = 102) being children under the age of 14 years. Salmonella species were detected in 37% (10/27) of water samples and geographic information system (GIS) mapping showed clustering of cases in Tswaing-Kgwaripe and Vlakplaas villages. Six isolates were available for WGS analysis, with resulting data showing that five of the six isolates were genetically related. Phylogenetic analysis showed that the five isolates clustered together were genetically related showing < 22 single nucleotide polymorphisms when compared to each other.

CONCLUSION

Molecular epidemiology of isolates suggests a common source outbreak, supported by the detection of Salmonella species from water sources. Consumption of water from contaminated open water sources, because of ongoing interruption of municipal water supply, was the likely cause of the outbreak. The investigation highlights the importance of consistent safe water supply and the ability of district surveillance systems to identify and contain outbreaks.