Summary

Many studies have investigated diarrhoeal disease in children <5 years of age, but diarrhoeal disease in older children, adults and the elderly are often overlooked. Data gaps in disease burden and aetiology make designing targeted interventions for these populations difficult.

This study examined trends in enteric pathogen prevalence in participants >5 years of age at selected sentinel sites in South Africa between 2018 and 2023. Among older children, adults and the elderly, our surveillance shows that those living with HIV (PLHIV; 53%; 331/621) constitute a large proportion of diarrhoeal cases. Enteric bacterial infections (31%) seemed to drive most of the disease burden, with EIEC/Shigella spp. detected frequently (20%). Enteric viruses were detected in 27% of cases >5 years of age presenting with diarrhoea but did not seem to be a major cause of disease in older individuals, likely due to acquired immunity.

The exception was norovirus genogroup II in PLHIV, and continued monitoring is recommended. There was also a significant decline in human adenovirus prevalence between 2018 and 2023, decreasing from 28% in 2020 to 3% in 2023. These declines may be related to the use of the Janssen Ad26.COV2.S SARS-CoV-2 vaccine, although additional investigation will be required. This study begins to provide a better understanding of the aetiology of diarrhoeal disease in older populations in South Africa and may inform targeted interventions.