A WPV case was defined as an AFP case for whom a stool specimen tested positive for WPV by virology, while a clinical compatible polio case was defined as an AFP case for whom stool specimens were missing or tested negative for WPV, but was determined to be polio-compatible by the provincial Polio Expert Committee of China after the standard 60-day follow-up examination. This evidence concerns the gene AFP and poliomyelitis.