Innovation

What lurks beneath: Treatment plants provide a citywide view, while samples taken from manholes brings the focus down to neighbourhood level.

Beneath Johannesburg’s streets, in pipes that stretch three metres across, the health of the city flows unseen. Wastewater is usually thought of as something to be managed and forgotten, but in Gauteng, it has become an information system, one that can detect outbreaks before people turn up at clinics. 

Fiona Els is an epidemiologist at the Gauteng City-Region Observatory (GCRO) and the National Institute for Communicable Diseases (NICD). She works on the national wastewater surveillance programme, which turns sewage into signals that can shape public health. “Before people even feel sick enough to go for a test, they already excrete the virus,” says Els. “We can see an outbreak coming two to three weeks before cases arrive at clinics, and then we can warn hospitals to prepare.”