AFP and poliomyelitis: In our circulation analysis, some of the prior detections by ES and AFP surveillance occurred in different provinces from the province from which the polio case was reported (i.e., cross-province detection); however, in sensitivity analyses, when we restricted genetically-similar matches to only those detected in the same province as the polio case, our observed results remained consistent–ES detected poliovirus circulating prior to the onset of the polio case months sooner on average than did AFP surveillance.