Nepal has strengthened its polio surveillance system with the establishment of a new environmental surveillance (ES) site in Birgunj Metropolitan City, Madhesh Province, in April 2026. This milestone underscores the country’s continued commitment to sustaining its polio-free status while enhancing early detection capacity.
ES involves collecting and testing sewage samples to check whether pathogens are present in communities. It acts as an early warning system, helping health authorities detect disease quickly, respond in time and improve outbreak preparedness and public health decisions. For poliovirus, this approach supports acute flaccid paralysis (AFP) surveillance by providing additional information on virus circulation in specific areas. It makes the overall surveillance system more sensitive and can identify silent transmission that might otherwise go unnoticed, strengthening preparedness and response efforts.
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Joint exploratory field visit conducted by senior laboratory and public health officials in Birgunj Metropolitan City, Parsa, Madhesh Province. Photo credit: WHO Nepal
In 2025, Nepal tested 169 sewage samples from nine ES sites across five provinces and investigated 594 AFP cases, with all results confirming no poliovirus circulation.
Despite these strong surveillance measures, Nepal remains at risk of poliovirus importation due to open borders and high cross-border population movement. In addition, pockets of suboptimal vaccination coverage continue to pose challenges, underscoring the need for sustained vigilance.
Against this backdrop, Birgunj was selected as a new ES site due to its high population mobility, status as a key international gateway between Nepal and India, dense urban setting and well-defined sewage catchment systems. With this addition, Nepal now operates 10 ES sites nationwide.
To operationalize the site, the National Public Health Laboratory (NPHL), with technical support from WHO Nepal and in coordination with the Provincial Public Health Laboratory (PPHL) in Madhesh Province, conducted a joint exploratory field visit and stakeholder consultation in Birgunj from 8–10 April 2026. Participants, including senior laboratory technologists, public health officials, municipal representatives and WHO personnel, assessed potential sewage collection sites based on population coverage, sustainability and accessibility.
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Stakeholder meeting in Birgunj Metropolitan City, Parsa, Madhesh Province, to disseminate findings from the joint exploratory field visit on the expansion of environmental surveillance sites. Photo credit: WHO Nepal
During the consultation, WHO technical experts emphasized the importance of maintaining high-quality ES systems and strong inter-agency collaboration.
Accordingly, Madhesh Province has designated focal persons from the Health Office, municipality, and laboratories to lead implementation. These personnel will be trained in standard operating procedures covering sample collection, biosafety, labeling, packaging, documentation and cold chain management. Collected sewage samples will be transported monthly to NPHL for processing and subsequently forwarded to the polio reference laboratory at the National Institute of Health in Thailand for testing.
ES collection from Birgunj is scheduled to commence in the second quarter of 2026. With continued technical oversight from NPHL, this expansion is expected to further strengthen Nepal’s polio surveillance system and generate robust evidence confirming the absence of poliovirus circulation, reinforcing the country’s commitment to remain polio-free.