Assessment of environmental surveillance for the detection of poliovirus implementation in the metropolitan districts of South Africa, 2020-2023.

Introduction: South Africa began using environmental surveillance (ES) in July 2019 to supplement acute flaccid paralysis surveillance. A study is evaluating sites in eight metropolitan health districts for performance improvement and expansion of ES within and across neighbouring countries.

Methods: we conducted a descriptive analysis of secondary ES to detect poliovirus supplemented with qualitative field visits and focused group discussions at 16 ES sites in the eight metropolitan districts of South Africa. The study covered data from January 2020 to December 2023, and tests were conducted to examine the relationship between practices and laboratory results.

Results: in 2021, the National Institute for Communicable Diseases (NICD) Laboratory received 567 ES samples for poliovirus detection, with 97.9% arriving within 72 hours of collection. Monthly sampling increased from 102 (18%) in 2020 to 184 (32.5%) in 2021, showing a 14.5% change with a p-value of 0.0085. There was no statistically significant difference in enterovirus isolation rates between sites trained virtually and in person in the long term, with a 16.5% difference and a p-value of 0.0977. Some ES sites showed high enterovirus isolation rates despite not having specific peak hours, suggesting operational variability in densely populated cities and other areas.

Conclusion: the ES assessment in South Africa has made progress in identifying enteroviruses at all sites. However, irregularities in monthly sampling and peak hours for sample collection need attention. The study suggests using a similar training approach in areas with accessibility challenges and updating guidelines with special consideration for major cities.