Wastewater surveillance (WWS) is a method that analyses pooled community wastewater through the organised sewage system or the unorganised drains and nalas for pathogen detection within a population. Disease surveillance in India through wastewater was initiated in Mumbai for Polio in 2001[1]. In this exercise, a systematic wastewater analysis was conducted to study the prevalence of the disease in India. More recently, the machinery detected one case of vaccine-derived polio virus-type 1 from a sewage sample collected from Kolkata in April 2022[2]. The emergence of SARS-CoV-2 and the emphasis on public health machinery to respond and find methodologies through which the virus can be tracked in the city/country supported the uptake of WWS. The ability to quantify the virus in wastewater and compare clinical cases helped provide the government with a week to 10-day lead time. WWS also helped the governments gauge the number of asymptomatic patients, which would be most certainly missed in clinical testing unless unbiased clinical sampling was done. For instance, in a study at CSIR- National Chemical Laboratory, analysis of their campus WWS showed the presence of signature mutation of the Omicron variant as early as Nov 2022[3].

How does it work?

Image Source:- Pune Knowledge Cluster

The pathogens in wastewater are detected by testing for their nucleic makeup in the sewage. The standard procedure is wastewater sample collection, nucleic acid extraction and amplification, followed by its testing to quantify pathogens with PCR-based methods or NGS used for variant detection. Given the nature of wastewater, the number of human and animal microbes, and many other components that end up in wastewater, the noise is significant. There is no standard methodology for disease detection, and more importantly, the lack of global and regional standards that identify a gold standard in testing creates hurdles in interpretation. Data standardisation in WWS is another obstacle. Systematic access to the wastewater samples is also dependent on permissions from the governments, and accessibility to the Sewage Treatment Plants in many Indian cities poses challenges.  

WWS in India in times of COVID-19 – a case study

The first successful detection of SARS-CoV-2 in India through wastewater was in Ahmedabad, Gujarat, in May 2020 from a Civic Hospital[4]. In the last four years, it has been adopted by several cities and by governmental agencies in India.  INSACOG (Indian SARS-CoV-2 Genomics Consortium), in 2022, extended their genomic database to include data collected through wastewater surveillance. Detecting the virus in wastewater gave decision-makers a lead time of 10-14 days. This time is vital for public health authorities to re-look at priorities, reallocate human resources and alert the medical fraternity. There is a need, however, to make systematic correlations to clinical cases. WWS especially showed significance in identifying silent waves of COVID-19. 

The potential of WWS

Post-COVID, there has been an international effort to leverage this cost-effective, non-invasive method of measuring disease incidence for many other diseases. Recently, a study in Ontario, Canada, used WWS for Respiratory Syncytial Virus (RSV). Quantification of the RSV in wastewater gave them a 12-day lead time to reduce the RSV burden, influence regional health system preparedness and understand variations in the community as novel RSV vaccines and monoclonal antibodies were used to reduce disease burden.[5] WWS has recently also been used extensively for the testing of Antimicrobial Resistance (AMR). Wastewater is considered a significant reservoir of AMR and studies have shown that the treatment of the sewage water doesn’t remove antibiotics, Antibiotic-resistant bacteria (ARBSs) and antibiotic-resistant genes (ARGs), causing havoc downstream[6]. Recent studies have focused on using WWS for quantifying AMR gene abundance, AMR distribution in reference to seasons and geographic presence and association with clinical samples[7]

Lessons from the past

While WWS for COVID-19 was successful, it taught us the gaps and identified areas that require our focus if this were to be implemented on a larger scale, such as a city, town, or locale across diseases and pathogens. We must focus on the challenges below to build a sustainable WWS system.

  1. A synchronised working partnership between the governmental departments (Health/Medical/Water/Sewage Board) and WWS group. 
  2. A comprehensive map of the cities’ sewage/open drains network. This is extremely important to make population inferences. 
  3. Classical surveillance and disease monitoring systems are overburdened and have significant underreporting. WWS allows public health officials to gauge the spread/prevalence of the disease. 
  4. Data and insights generated through WWS and traditional surveillance techniques must be integrated to enable decision-making through this data[8].
  5. A better understanding of disease shedding patterns for diseases chosen for WWS.

Backing WWS with the power of science and technology

Image Source:- Pune Knowledge Cluster

Newer technologies in the field of omics, molecular and sequencing technologies are likely to impact the course of WWS. Metagenomics is currently used to screen a wide range of viruses in wastewater. Identification of co-infecting organisms during outbreak conditions, novel pathogens, and viral composition in complex matrices through metagenomics in WWS has been possible. Despite the progress to identify viral pathogens, PCR is still done to corroborate results due to the presence of bacteria, sequencing limitations, errors in sequence analysis and alignment tools[9]. Development and deployment of low-cost, rapid sensors have shown potential. For example, in Uganda, paper-based microfluidics for DNA diagnostics was used for the detection of malaria in WW. Another microfluidic device has been developed and tested for the rapid and on-site detection of SARS-CoV-2 and Influenza[10]. This device detects the pathogens in less than 1.5 hours. It must be acknowledged that these are indicative studies. The rapid and accurate quantification of pathogens from wastewater and population-level extrapolation remains a challenge.

The way forward

Leveraging the learnings from the WWS of COVID-19, we can use this as a precautionary tool to understand the diseases prevalent in a city, locality, and community. There is ample research to detect pathogens such as H1N1, H3N2, RSV, Typhi and AMR through WWS. The success of WWS as an early warning would be when information is disseminated to stakeholders such as doctors, public health officials and local municipalities. Countries such as Australia, Belgium, Canada, Chile, Finland, France, USA have integrated WWS into their national machinery[11]

The Alliance for Pathogen Surveillance (APSI)[12] in India has demonstrated that there is strength in partnership and knowledge sharing to support WWS. The APSI network has successfully built a consortium of stakeholders through which shared protocols, best practices, reporting methods and governmental discussion happen. APSI’s model was set up with the intention of making WWS accessible to government agencies and creating a working model of WWS which the government can implement pan-India. Results and data from the consortium can be analyzed and extrapolated to an Indian context. 

The sustainability of WWS is dependent on integrating into the existing machinery at the municipality level or through the Integrated Disease Surveillance Program (IDSP). Under the Ayushman Bharat Health Infrastructure Mission, the government has proposed the development of Metropolitan Surveillance Units (MSU), which aim to support and integrate disease surveillance at the city level. Integrating WWS into the public health system through these units would be ideal. The mandate of the MSU is to function as a hub for disease surveillance. WWS can be leveraged along with our current passive and active surveillance methodologies to build a robust surveillance system that supports the early detection of pathogens.

About the Author:

Priyanki Shah has over 15 years of experience within the health ecosystem, traversing through private and public. She has a Master’s in Molecular Medicine and Microbiology and is a qualified Project Manager. She specialises in driving collaborations between government, academics, and philanthropies to generate evidence and knowledge that drives public health work. She specialises in the implementation and management of large-scale public health programs.

References:

  1. Environmental Surveillance for Polioviruses in the Global Polio Eradication Initiative. The Journal of Infectious Diseases, Volume 210, Issue suppl_1, November 2014, Pages S294–S303, https://doi.org/10.1093/infdis/jiu384
  2. https://www.who.int/india/news/detail/17-06-2022-investigation-of-the-vaccine-derived-polio-virus–found-in-sewage-sample-in-kolkata
  3. Campus Sewage Water Surveillance based dynamics and infection trends of SARS-CoV-2 variants during third wave of COVID-19 in Pune, India 
  4. First proof of the capability of wastewater surveillance for COVID-19 in India through the detection of the genetic material of SARS-CoV-2. Sci Total Environ. 2020 Dec 1:746:141326.
  5. Wastewater-based surveillance identifies the start of the pediatric respiratory syncytial virus season in two cities in Ontario, Canada Front. Public Health, 26 September 2023, Sec. Infectious Diseases: Epidemiology and Prevention. Volume 11 – 2023
  6. Surveillance, distribution, and treatment methods of antimicrobial resistance in water: A review, Science of The Total Environment, Volume 890, 10 September 2023, 164360
  7. Systematic review of wastewater surveillance of antimicrobial resistance in human populations. Environ Int. 2022 Apr; 162: 107171. 
  8. Wastewater surveillance of pathogens can inform public health responses. Nature Medicine volume 28, pages 1992–1995 (2022) 
  9. Identification of multiple potential viral diseases in a large urban center using wastewater surveillance. Water Research, Volume 184, 1 October 2020, 116160
  10. Low-cost and rapid sensors for wastewater surveillance at low-resource settings, Zhugen Yang, Nature Water volume 1, pages 405–407 (2023)
  11. Wastewater Surveillance for Disease Epidemiology: Embracing the Chaos and the Uncertainties. Indian Public Policy Review 2023, 4(6): 45-65.
  12. https://data.ccmb.res.in/apsi/

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