What is the role of environmental surveillance in polio eradication?

• A. To monitor clinical cases reported by health facilities.
• B. To screen blood for poliovirus antibodies.
• C. To measure population immunity through serosurveys.
• D. To detect circulation of poliovirus in sewage, including vaccine-derived strains, enabling early outbreak detection.

Answer: (D)

Environmental surveillance focuses on detecting poliovirus in the sewage system. By sampling wastewater from communities, it can reveal whether the virus is circulating even if no child has paralysis or reported cases. This matters because most poliovirus infections don’t cause obvious symptoms, so relying only on clinical reporting can miss ongoing transmission. It also detects vaccine-derived strains, which shed from vaccinees and can indicate transmission of those strains in the population. When a positive sewage sample is found, public health teams can respond quickly with targeted vaccination campaigns, intensified case finding, and enhanced surveillance to prevent outbreaks. This approach complements, rather than replaces, clinical AFP surveillance, providing a sensitive early warning system.