[Investigation of a Patient with Pre-vaccine-derived Poliovirus in Shandong Province, China].

To analyze the genetic characteristics of a polio-I highly variant vaccine recombinant virus in Shandong Province (China) in 2011 and to identify isolates from healthy contacts, two stool specimens from one patient with acute flaccid paralysis (AFP) and 40 stool specimens from his contacts were collected for virus isolation. The complete genome of poliovirus and VP1 coding region of the non-polio enterovirus were sequenced. Homologous comparison and phylogenetic analyses based on VP1 sequences were undertaken among coxsackievirus (CV) B1, CV-B3 isolates, and those in GenBank. One poliovirus (P1/11186), CV-A4 and CV-A8 were isolated from the AFP patient; one CV-A2, Echovirus 3 (E-3), E-12 and E-14, ten CV-B1, and five CV-B3 strains were isolated from his contacts. These results led us to believe that there may be a human enterovirus epidemic in this area, and that surveillance must be enhanced. P1/11186 was a type-1 vaccine-related poliovirus; it combined with type-2 and type-3 polioviruses in 2A and 3A regions, respectively. There were 25 nucleotide mutations with 9 amino-acid alterations in the entire genome. There were 8 nucleotide mutations with 5 amino-acid alterations in the VP1 region compared with the corresponding Sabin strains. Homology analyses suggested that the ten CV-B1 isolates had 97.0%-100% nucleotide and 98.9%-100% amino-acid identities with each other, as well as 92.6%-100% nucleotide and 99.2%-100% amino-acid identities among the five CV-B3 isolates. Phylogenetic analyses on the complete sequences of VP1 among CV-B1 and CV-B3 isolates showed that Shandong strains, together with strains from other provinces in China, had a close relationship and belonged to the same group.