Wastewater-based epidemiology offers blueprint for post-pandemic preparedness

India’s experience with COVID-19 highlighted the limits of clinical reporting systems, particularly in detecting local epidemic waves. Now, a group of researchers argue that wastewater-based epidemiology could fill those gaps, offering a sustainable and affordable model for disease surveillance. The study introduces a cost-sensitive approach that could transform epidemic preparedness in resource-limited countries.

Published in COVID, the paper “Wastewater-Based Epidemiology Monitoring for Endemics Like COVID-19 in India Through a Bi-Phase Detection Approach” is based on extensive testing of wastewater samples in Jaipur between June 2021 and July 2022. By comparing detection methods and transport conditions, the authors propose a hybrid strategy that balances sensitivity with affordability.

How reliable is wastewater surveillance for detecting epidemic waves?

The researchers collected 1,050 wastewater samples from ten treatment plants across Jaipur to assess the performance of wastewater-based epidemiology in tracking the presence of SARS-CoV-2. Their findings confirmed that wastewater monitoring could capture epidemic cycles that were not fully reflected in official case reports.

Two local waves were identified: a minor surge during August and September 2021, and a more pronounced wave between December 2021 and February 2022. In untreated wastewater samples, 62.9 percent tested positive for the virus, underscoring the method’s reliability. The most consistently detected genetic markers were the N and ORF1ab genes, while other targets showed less sensitivity.

This evidence suggests that wastewater testing can act as an early warning system, identifying rises in viral activity even when clinical testing data is incomplete or delayed. Such early detection is particularly valuable for countries with under-resourced healthcare systems, where clinical surveillance may miss localized outbreaks.

What detection methods and transport systems work best?

The study compares the effectiveness of two main detection methods: the direct method and the polyethylene glycol (PEG) concentration method. The PEG approach proved slightly more sensitive, detecting around two percent more positive cases than the direct method. However, the cost difference was dramatic. The PEG technique was found to be 330 times more expensive than the direct method, raising questions about its practicality for routine use.

The team also tested whether samples needed to be transported under a cold chain to preserve viral integrity. Surprisingly, results showed no significant difference between samples transported under cold conditions and those moved at ambient temperature. This finding carries major cost implications, as ambient transport eliminates the need for expensive logistics infrastructure while still ensuring reliable detection.

By weighing sensitivity against financial and operational constraints, the researchers concluded that the direct method, combined with ambient transport, is the most viable option for large-scale, year-round surveillance.

How can costs and sensitivity be balanced in long-term monitoring?

Recognizing the trade-offs between accuracy and affordability, the authors propose a bi-phase detection model. Under this framework, the direct method would be used for routine, year-round monitoring to keep costs manageable. During periods when case numbers rise or a new wave is suspected, authorities could switch temporarily to the more sensitive PEG method to capture as much data as possible.

This flexible system ensures that resources are not wasted during stable periods but can be intensified when the risk is higher. For low- and middle-income countries, the approach offers a way to maintain continuous surveillance without overwhelming public health budgets.

The model is not limited to COVID-19. The authors argue that it could be applied to other endemic viruses in India and similar regions, providing a scalable strategy for broader public health monitoring. By institutionalizing wastewater-based epidemiology, policymakers could strengthen epidemic preparedness and response capacity long after the immediate pandemic has subsided.