By Rachel V. Thomas
New Delhi, May 14 (IANS): Wastewater surveillance, which gained popularity during the Covid-19 pandemic, is an essential tool in comprehensive public health and lifestyle monitoring, and its need and benefits exceed that of the SARS-CoV-2 virus, said experts on Sunday.
During the last three years of the Covid pandemic, wastewater surveillance proved to be the most cost-effective tool as it helped provide preliminary insight on the infection status in resource-constrained systems, particularly in a highly populated country like India.
The surveillance tested a pooled sample of a large portion of the city population.
"People in the community infected with Covid would shed the virus in their stools and scientists measured and tested wastewater for the presence of SARS-CoV-2 to find the extent of the virus spread in the community - whether it is increasing, staying the same or which variant is circulating, etc," Shirish Harshe, Senior Technical Specialist in public health organisation Precision Health A. Swasti, told IANS.
"The sewage surveillance is an indicative surveillance tool and provides a signal that can be detected and tracked to make quick and pre-emptive decisions in preventing and containing infectious disease incidences, thereby building the city's resilience in tackling ever-growing issues of emerging infectious diseases," he said, adding "the need for wastewater surveillance exceeds SARS-CoV-2".
In India, a city-wide wastewater surveillance system, also a first in Asia, was established in Bengaluru in May 2021 by Precision Health Platform assisted by several local and government bodies.
Precision extended the surveillance beyond Covid to explore pathogens like Influenza A, B and H1N1, even Mpox, pharmaceutical drugs, and antimicrobial resistance genes. The platform aims to expand surveillance efforts in 25 cities across India and South East Asia.
Conventional detection methods focus on individuals, rendering testing cumbersome, slow, expensive, and mostly reactive. The tools rely on symptoms, clinical tests, surveys and questionnaires. Testing each and every citizen for individual testing is a highly costly endeavour, both in terms of funds and time.
Wastewater surveillance, on the other hand, is highly cost effective as it involves the analysis of population data collectively through a few wastewater samples. Thus, it is quick and much less cumbersome than conventional techniques.
It can also predict disease outbreaks faster than the existing health assessment tools and identify hot infection spots to respond better to future outbreaks. Wastewater Based Epidemiology (WBE) dashboards can function as tools to alert the public regarding the spread of diseases.
"WBE is an essential tool in comprehensive public health and lifestyle monitoring. In the long term, WBE will be employed to fill the gaps in clinical testing of the health of a population. The availability of a cost-effective system for disease surveillance and health monitoring will benefit the health sector," Prof. T. Pradeep, Institute Professor, Department of Chemistry, IIT Madras, told IANS.
"Given the densely populated cities in India, it is essential to establish surveillance and early warning systems to control disease spread. WBE offers a surveillance tool that can predict the spread of diseases much before the clinical data," he added.
However, owing to less clarity among public health officials, the government and municipal corporations, the possibilities for health monitoring through the WBE are much less explored yet.
"There is a lack of national and state policies on WBE, and lack of capacities for regular testing, sense-making platforms, and communication," Harshe said.
"In addition to this, the infrastructure of drainage systems in different cities is not uniform," he noted.
Citing environmental scientist Sudipti Arora's article in Nature journal, he stated that unlike western countries, the sewerage system in India is fragmented -- only about 33 per cent is connected, and of the rest, only 38 per cent use septic tanks.
"The rest of the population use non-sewered drains, which means their waste is disposed through open stormwater drains which doesn't help in detecting hotspots," Harshe told IANS.
Yet the applications of WBE in comprehensive public health monitoring are versatile.
"These include the surveillance of non-infectious diseases through the evaluation of biomarkers released in wastewater through the consumption of pharmaceuticals. The WBE surveillance of antidepressants and psychoactive medicines can be correlated to the overall mental health of the population monitored. The effect of public health policies being implemented will be evaluated at the population level through WBE," Prof. Pradeep said.
The experts recommended a more sustainable model of environmental surveillance which will help governments by providing quick and evidence based decisions on preventing and preparing for the future pandemic.