Why in news?
The Indian Council of Medical Research announced in August 2025 that it will expand wastewater‑based epidemiology to 50 cities and monitor at least 10 different viruses. The initiative aims to provide early warning for outbreaks and complement clinical surveillance.
What is wastewater surveillance?
Wastewater, or sewage, contains traces of pathogens excreted in human waste. By collecting and analysing samples from sewer systems, scientists can estimate the prevalence of diseases in a community without testing individuals. During the COVID‑19 pandemic many countries used this method to track viral spikes.
Steps in the process
- Collection: Samples are taken from sewage treatment plants or specific sewer pipes at regular intervals.
- Concentration and testing: The water is filtered and treated to concentrate viral particles. Molecular techniques such as RT‑PCR detect genetic material of viruses like SARS‑CoV‑2, polio, influenza, hepatitis A and E, dengue and others.
- Data analysis: Scientists compare viral loads over time to identify increases that may precede clinical cases. Authorities can then issue advisories or ramp up vaccination and testing.
- Public health action: Results inform resource allocation, such as deploying mobile clinics or spraying mosquitos in areas where dengue virus levels are rising.
Advantages and challenges
Wastewater surveillance is cost‑effective, anonymous and able to detect asymptomatic infections. However, it requires well‑maintained sewer networks and timely laboratory analysis. Data must be interpreted carefully, as rain and industrial effluents can dilute samples. Expanding the programme will build India’s capacity to respond rapidly to future epidemics.