Molecular Epidemiology and Recombination of Human Enteroviruses from AFP surveillance in Yunnan, China from 2006 to 2010

The study represents the genetic overview of non-polio enteroviruses (NPEV) isolated from acute flaccid paralysis (AFP) cases in Yunnan Province from 2006 to 2010. Molecular typing based on VP1 nucleotide sequence was carried out on 98 NPEV isolates, and 33 serotypes were identified. EV-B was detected most frequently with an overall prevalence of 71.4%, followed by EV-A (18.4%) and EV-C (10.2%). No EV-D was identified. NPEV positive rate was higher in children <3 years of age and in summer and autumn months. Clinically, 68.4% patients presented with fever, and 16 cases (16.3%) were classified as Guillain-Barré syndrome, followed by myositis (13.3%). The phylogenetic analysis on the VP1 and 3D regions of prevalent serotypes provided evidence for recombination events among them. EV-A71, an important pathogen previously demonstrated to be associated with paralysis, had also been detected (n = 8) in this study and they all belonged to genotype C4. Great genetic divergence between Yunnan isolates and strains from other regions of the world was revealed. The findings of the study are of great importance for further research on molecular evolution of EV under the circumstance of no specialized EV surveillance system in China.