Wastewater as an Early Warning System for Epidemics: Evidence from Nepal and the Philippines

The Asian Development Bank, with support from the Government of Austria and research partners including Emory University, piloted wastewater-based epidemiology in Nepal and the Philippines to show how sewage can provide early, population-wide signals of infectious diseases such as COVID-19 and cholera. The pilots demonstrated that wastewater surveillance can complement traditional health systems, improve outbreak preparedness, and support faster, better-targeted public health responses when integrated into routine disease monitoring.

The Asian Development Bank (ADB), with financial support from the Government of Austria, partnered with the Center for Global Safe Water, Sanitation, and Hygiene at Emory University to pilot wastewater-based epidemiology in Nepal and the Philippines. Working with local institutions such as Tribhuvan University, the Kathmandu Valley Water Supply Management Board, Kathmandu Upatyaka Khanepani Limited, and the Manila Water Company, Inc., the initiative explored how wastewater could be used as a practical and reliable tool for monitoring infectious diseases at the community level. The project emerged from lessons learned during the COVID-19 pandemic, when traditional disease surveillance struggled due to limited testing, delayed reporting, and unequal access to healthcare.

Wastewater-based epidemiology, or WBE, measures genetic material from pathogens that people shed in their feces and urine. Because wastewater reflects the health status of entire populations, it can detect rising infection trends earlier than hospital-based systems. The report shows how WBE can complement routine surveillance, especially in cities where many people are asymptomatic or unable to seek medical care.

Why Wastewater Surveillance Matters

The COVID-19 crisis revealed that relying only on clinical testing leaves dangerous gaps in disease detection. WBE helps close those gaps by offering a noninvasive, population-wide snapshot of infection levels. Importantly, the method does not depend on individuals choosing to get tested. Instead, it captures data from everyone connected to sanitation systems. The report highlights that WBE can detect changes in infection trends days or even weeks before case numbers rise, giving authorities valuable time to respond.

Although SARS-CoV-2 was the main focus of the pilots, the technology is not limited to one disease. Using modern laboratory techniques, a single wastewater sample can be tested for multiple pathogens at once, including cholera, typhoid, and dengue. This flexibility makes WBE a cost-effective tool with long-term value beyond pandemics.

Building Capacity in Kathmandu, Nepal

In Nepal, the pilot revealed that existing laboratory facilities were not suitable for advanced wastewater testing. Instead of upgrading an old chemistry lab, partners chose to build a new molecular biology laboratory designed to international standards. ADB funded the construction through a separate project, while the WBE pilot supported equipment, training, and operations. Emory University provided technical guidance, and Tribhuvan University anchored the work locally.

The Kathmandu pilot went beyond COVID-19 by including Vibrio cholerae, reflecting Nepal’s recurring cholera outbreaks. Local teams were trained in sampling, laboratory testing, quality control, and data interpretation. Weekly wastewater samples were collected from selected river points, sewer outfalls, and treatment plant inflows. Results showed frequent detection of SARS-CoV-2 and demonstrated that wastewater surveillance was both feasible and useful in Nepal, even in a challenging sanitation environment.

Scaling Surveillance in Metro Manila, Philippines

In the Philippines, the pilot took place in Metro Manila’s east zone, where sanitation systems include both centralized sewerage and septic tanks. The Manila Water Company already operated a modern laboratory, allowing the project to focus on improving methods rather than building new infrastructure. Emory University assessed laboratory readiness and helped refine testing protocols suited to local supply chains.

Sampling sites were carefully chosen using sewer maps and population data to ensure broad and fair coverage. Over several months, wastewater and fecal sludge samples were tested for SARS-CoV-2, producing near real-time data on infection trends. A digital dashboard translated these results into visual insights that public health officials could easily understand and use. This allowed authorities to identify hotspots and align wastewater data with reported COVID-19 cases.

Lessons, Challenges, and the Road Ahead

The pilots revealed important challenges. There are no global standard methods for wastewater surveillance, making comparisons difficult. Laboratory supplies can be slow to procure, and mixed sanitation systems complicate sampling and data interpretation. Wastewater data can also appear noisy, requiring careful explanation to health officials unfamiliar with environmental surveillance.

Despite these challenges, the report concludes that wastewater-based epidemiology is a powerful and scalable public health tool. Success depends on strong collaboration between health and sanitation sectors, sustained investment in laboratories and training, and clear strategies for using data in decision-making. Looking forward, the report calls for integrating WBE into routine disease surveillance, expanding multipathogen monitoring, and improving communication with health authorities. If institutionalized properly, wastewater surveillance can strengthen epidemic preparedness and help protect urban populations across Asia and the Pacific.