Significant blind spot in wastewater-based surveillance

Wastewater-based surveillance for assessing public health risks may include a significant “blind spot”, new research shows.

While current monitoring systems rely almost exclusively on bacterial indicators, a new study from the Harbin Institute of Technology suggests that this narrow focus overlooks the complex biological drivers within water treatment plants.

The research, published in Biocontaminant by Shu-Hong Gao’s team, reveals that persistent viral communities within wastewater treatment plants (WWTPs) serve a "double-edged" purpose.

On one hand, these viruses influence the breakdown of pollutants. On the other, they facilitate the spread of antibiotic resistance.

The study argues that existing surveillance protocols, which prioritise bacterial markers, likely overlook significant viral hazards. They may also miss opportunities to make reclaimed water systems safer.

Antibiotic resistance

Using an advanced metagenomic workflow, researchers looked at 28 samples across different treatment configurations.

They identified 99 viral families across the entire treatment process.

Certain taxa, most notably Peduoviridae and Casjensviridae, showed a high prevalence from the moment water entered the plant until it left as effluent.

This proves that viral populations are not just confined to the "sludge" (the solid waste). Instead they stay active throughout the entire liquid treatment process.

Crucially, the study found that viral behaviour does not mirror traditional indicators like Escherichia coli (E. coli).

Instead, viruses closely track opportunistic pathogens like Pseudomonas aeruginosa.

This suggests that Pseudomonas could serve as a far more accurate indicator for assessing virus-associated risks than the bacteria we currently track.

Functional analysis further revealed 117 auxiliary metabolic genes (AMGs) that help viruses manipulate the metabolism of their hosts to remove pollutants during biological treatment stages.

However, these same genetic pathways were also linked to the spread of antibiotic resistance genes.

More effective tools

Because the primary hosts for these viruses are phyla rich in multidrug-resistant pathogens, the researchers argue that viruses must be integrated into routine biological monitoring.

By identifying these persistent viral-pathogen pairs, the industry can develop more effective tools for evaluating how well a treatment system is performing.

Further this may help provide better early warning signals for emerging health threats in recycled water.