Researchers have increased the understanding of diarrheal disease in older populations in South Africa.

A study examined trends in enteric pathogen prevalence in participants older than 5 years of age at seleced sites between 2018 and 2023. Findings were published in the Public Health Bulletin of South Africa.

Data were analyzed from two systems: the Diarrhoeal Diseases Sentinel Surveillance (DDSS) and the African Network for Improved Diagnostics, Epidemiology, and Management of Common Infectious Agents (ANDEMIA). 

A total of 677 diarrhea cases and 183 controls were enrolled across sub-Saharan Africa. The majority of cases were from hospitals and had a median age of 34. The number of sites varied from three in 2018 to 12 in 2022.

Detected trends

Viruses were detected in 27 percent of cases, bacteria in 31 percent, parasites in 8 percent, and mixed infections in 17 percent. Notable declines were observed in Norovirus, adenovirus, Cryptosporidium, and Shiga toxin-producing E. coli (STEC). No significant changes were seen for other pathogens like Salmonella or Giardia lamblia.

Enteric viruses were detected in 186 of 677 cases above the age of 5. Norovirus prevalence peaked at 11 of 55 in 2018 and eight of 61 in 2020. However, there was an overall decrease in cases between 2018 and 2023.

Bacteria were detected in 209 of 677 patients, parasites in 56 patients, and mixed pathogen infections in 114 patients.

Major declines in prevalence were noted for Cryptosporidium, dropping from 10 percent (7/55) in 2018 to 4 percent (6/161) in 2023. STEC declined from 7 percent (9/138) in 2019 to 1 percent (1/161) in 2023.

No significant trends in the circulation of EIEC/Shigella, Campylobacter jejuni/coli/lari, or Salmonella were noted.

Most of the diarrheal disease burden in older children, adults, and the elderly seemed to be driven by bacteria, detected in roughly a third of patients in the study, said scientists.

Getting data to help with interventions
EIEC/Shigella detection was also significantly associated with diarrhea and contributed to disease in both the clinic and hospital settings.

Increased detection of Cryptosporidium, Campylobacter, STEC, and Giardia lamblia in hospital cases suggests either that these pathogens may cause slightly more severe diarrheal symptoms, or their involvement in mixed pathogen infections may result in more severe disease.

Researchers said diarrheal surveillance in older children, adults and the elderly provides insight into disease in older populations in South Africa and could assist in guiding intervention strategies.

Recommendations included continued enteric pathogen surveillance in older participants to investigate the role of bacteria in diarrheal disease, levels of antimicrobial resistance in enteric pathogens in South Africa, and how mixed infections impact disease severity.