Integrating environmental and clinical surveillance for typhoid: insights from a prospective wastewater surveillance study in urban India
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Publication: Mohan et al., The Lancet Microbe (2026)
Overview
This prospective study evaluated whether wastewater surveillance for Salmonella enterica serovar Typhi (S. Typhi) reflects clinical typhoid burden in an endemic urban setting. Researchers collected 1,446 wastewater samples from 50 locations in Vellore, India, before introduction of a typhoid conjugate vaccine (TCV). Grab samples were concentrated using Nanotrap® Microbiome A Particles (NMP-A) and compared with conventional Moore swab passive sampling. S. Typhi was detected by multiplex qPCR targeting ttr, staG, and tviB, and wastewater results were compared with blood culture-confirmed clinical cases.
Key Findings
Nanotrap particles significantly improved S. Typhi detection
S. Typhi was detected in 8.3% (60/723) of grab samples processed with NMP-A, compared with 2.8% (20/723) of Moore swabs.
After adjustment for typhoid incidence, fecal contamination, rainfall, and spatiotemporal effects, the NMP-A method had 4.46× higher odds of detecting S. Typhi than the Moore swab method (95% CI 2.28–8.73; p<0.001).
The authors conclude that NMP-A outperformed Moore swabs for detecting S. Typhi-related gene targets in low-volume wastewater samples.
Wastewater detection correlated with clinical typhoid burden
During the six-month surveillance period, 207 blood culture-confirmed typhoid cases were recorded.
Wastewater S. Typhi positivity correlated significantly with clinical incidence across all wastewater catchments (ρ=0.44; p=0.001) and was stronger in the 37 non-overlapping catchments (ρ=0.57; p<0.0001).
Every 10-fold increase in clinical typhoid incidence was associated with 2.43× greater odds of detecting S. Typhi in wastewater.
Wastewater surveillance identified spatial patterns of disease
Clinical typhoid cases clustered primarily in northeastern Vellore during an outbreak between March and May 2023.
Spatial modeling showed higher predicted wastewater S. Typhi detection in and around areas with greater clinical case density and identified typhoid hotspots, supporting the potential of wastewater surveillance for geographically targeted monitoring.
Human fecal load influenced detection
Higher concentrations of HF183, a human-associated Bacteroides fecal marker, were significantly associated with S. Typhi detection.
This finding highlights the importance of accounting for human fecal content when interpreting wastewater pathogen surveillance results.
Implications for Nanotrap Technology
This study provides strong field evidence for Nanotrap Microbiome A Particles as an effective concentration technology for bacterial pathogen surveillance in wastewater. Importantly, the performance advantage was demonstrated within a large, prospective surveillance program rather than only through laboratory-spiking experiments. NMP-A enabled greater S. Typhi detection from 40 mL grab samples and was strongly associated with improved detection after adjustment for environmental and epidemiological variables. The results support Nanotrap technology as a practical component of wastewater-based epidemiology programs for monitoring enteric pathogens and evaluating public health interventions.
Conclusion
The authors conclude that wastewater S. Typhi detection correlates with clinical typhoid incidence and can complement conventional disease surveillance in endemic communities. Of particular relevance to Nanotrap performance, NMP-A processing provided 4.46× higher adjusted odds of S. Typhi detection than Moore swab sampling, demonstrating a substantial advantage for pathogen concentration from low-volume wastewater samples. The study supports combining Nanotrap-enabled wastewater surveillance with clinical data to identify transmission hotspots, guide targeted vaccination and sanitation interventions, and potentially monitor the population-level impact of typhoid conjugate vaccine programs.
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