Fig. 1From: Vaccine-derived poliovirus surveillance in China during 2001–2013: the potential challenge for maintaining polio free statusThe number of children from whom VDPVs were isolated by year of identification and the types of children (VDPV case, non-polio AFP case and healthy population) in China during 2001–2013. VDPV, vaccine-derived polioviruses; AFP, acute flaccid paralysis; healthy population, contacts of AFP cases or healthy subjectsBack to article page