Daily prevalence of SL1-3 over time in Bihar province, India. The proportion of NP-AFP children positive for SL1 (A), 2 (B), and 3 (C) are shown by day of stool collection (solid lines). Triangles at the bottom of the panels show when SIAs were done, with the colors indicating vaccine used (tOPV containing OPV1, 2, and 3 in black, and bOPV containing OPV1 and 3 in green). OPV detection rates pulse very rapidly and briefly after SIAs. Between campaigns, detection rates are sporadic and of low prevalence, compatible with detecting SL from routine immunization that is continually being administered to children less then 1 year of age. NP-AFP = non-polio acute flaccid paralysis. OPV = oral poliovirus vaccine. SIA = supplementary immunization activity. SL = Sabin-like poliovirus.