What is the advantage of environmental surveillance in detecting poliovirus transmission?

• A. It measures population immunity directly through serology.
• B. It detects poliovirus only when clinical paralysis is present.
• C. It can detect circulation even in the absence of clinical cases, enabling rapid response and outbreak prevention.
• D. It replaces stool sampling in outbreak investigations.

Answer: (C)

Environmental surveillance looks for poliovirus in wastewater, catching what people shed into the system. Since many poliovirus infections don’t lead to paralysis, relying on clinical cases alone misses most transmission. By testing sewage, we can detect that the virus is circulating even when there are no illnesses prompting investigation, which lets health authorities respond quickly with targeted immunization and enhanced monitoring to prevent outbreaks. It doesn’t measure how immune people are (that would require serology), and it doesn’t rely on clinical paralysis, nor does it replace stool sampling or outbreak investigations—it's a complementary tool that signals circulation earlier and more broadly.