Wastewater-based surveillance has become a vital tool in public health monitoring, drawing on years of environmental surveillance efforts for pathogens like poliovirus. The majority of the wastewater surveillance conducted across the globe is mostly focused on monitoring single pathogens. The ongoing wastewater surveillance in Vellore City under the Department of Community Health since 2022, is mainly aimed at establishing baseline detection rates across different sampling sites for Salmonella typhi and Salmonella paratyphi A in the environment and monitoring longitudinal trends after phased TCV introduction in the study area as part of the Vellore Typhoid Vaccine Impact Trial.

Wastewater surveillance for Salmonella typhi and Salmonella paratyphi A

This proposal will leverage the existing environmental surveillance to a multiple-pathogen-based environmental surveillance model. In this proposal, we plan to extend the current Salmonella typhi and Salmonella paratyphi A surveillance at 20 sites from the urban wards, for an additional 30 months after the extension of current surveillance at 54 sites for an additional two months (August-September 2025). These 20 sites will be selected based on the previous performance in detecting Salmonella typhi and suitability for monitoring other pathogens.

Wastewater surveillance for avian influenza

In addition, we will implement wastewater (WW) surveillance for avian influenza. Fortnightly WW samples will be collected from 50 sampling locations (predominantly urban with important rural landmarks) on the sewage networks, poultry markets, and large retail poultry shops, and swabs from bird markets (surface swabs of cages, fecal samples, areas with fecal contamination) for a period of 32 months. This surveillance will allow us to detect the circulating strains of the influenza virus in the study area, study temporal trends, and compare rural-urban prevalence.

Wastewater surveillance for Vibrio cholerae

For Vibrio cholerae, we will be collecting fortnightly WW samples from 25 community sampling locations (20 urban and five rural) in Vellore for 32 months. Baseline rates of environmental detection of Vibrio cholerae will be estimated and this will enable urban and rural comparisons.

Serosurveillance surveillance for Vibrio cholerae

Additionally, we will be conducting a longitudinal serosurvey among 1080 rural and 1080 urban participants to estimate the seroincidence of Vibrio cholerae in the community by assessing the levels of Vibrio cholerae-specific antibodies. We will be collecting dried blood spots at baseline, 4-6 months, and 10-12 months into the study for this purpose. We will be assessing the association between the seroincidence of cholera and overall WW positivity, adjusting for the population size.

Wastewater surveillance for MTBC and AMR genes associated with MTB resistance (MDR and XDR)

We will also collect fortnightly WW samples to detect MTBC and AMR genes associated with MTB resistance (MDR and XDR), to monitor trends in the five rural and the 20 urban wastewater sampling sites for 32 months.

Community burden of pulmonary tuberculosis and drug-resistant tuberculosis

A community screening based on symptoms for pulmonary tuberculosis (PTB) will be conducted among all individuals above the age of 15 years from ~20,000 families in urban areas and all families from rural areas (three or four villages of Kaniyambadi block bordering Jawadhi hills) where wastewater surveillance is implemented. A sputum sample will be collected from those who are positive for symptoms of PTB from their houses and will be processed by the GeneXpert test, a highly advanced molecular diagnostic test that detects PTB and determines drug resistance, especially for rifampicin, which can indicate the presence of multi-drug-resistant TB. Samples testing positive by the GeneXpert test will be tested using the Xpert MTB/XDR assay, which can detect extensive drug resistance.