What role does environmental surveillance play in polio eradication?

• A. Sewage testing detects circulating poliovirus, including silent transmission, guiding outbreak response and verification of interruption of transmission.
• B. It replaces laboratory testing.
• C. It detects only vaccine strains.
• D. It is not useful in the absence of clinical cases.

Answer: (A)

Environmental surveillance uses sewage testing to look for poliovirus shed by infected people, including those with no symptoms. This provides a population-wide signal of whether the virus is circulating, even when there are no reported cases or paralysis. By detecting wild poliovirus and vaccine-derived polioviruses in wastewater, health authorities can rapidly identify areas with transmission, guide targeted immunization campaigns and outbreak responses, and track progress toward interruption of transmission. It also serves as an important tool in verification processes for declaring a region polio-free, helping confirm when transmission has ceased across a community.

It does not replace laboratory testing or clinical surveillance; instead, it complements them by catching circulation that might be missed if we rely only on reported cases. It is useful even in the absence of clinical cases, because silent transmission can occur, and environmental signals help ensure we don’t overlook ongoing circulation.