The CDC is expanding polio wastewater surveillance to some counties in Michigan and Pennsylvania with low vaccination rates and connections to the New York counties that had poliovirus detections.
It will be interesting to see what is found. After the case in Rockland county, New York, there was poliovirus found in the wastewater in several New York counties with low vaccination rates.
Polio has a lot of silent transmission. Most cases are non-paralytic and cause only mild symptoms. When a paralytic polio case occurs, you can be assured there have been hundreds to thousands of other polio infections.
Fortunately the polio vaccine is extremely effective at preventing poliomyelitis.
Polio is now only endemic in two countries globally, it would be awful to see a setback in the eradication campaign due to low vaccination.