Identification and genetic characteristics of non-polio enteroviruses isolated from patients with acute flaccid paralysis in 2015, Yunnan province, China

Abstract

Objective To investigate the virus-carrying rate of non-polio enteroviruses (NPEV) in patients with acute flaccid paralysis (AFP) in Yunnan province of China in 2015 and to analyze the genetic characteristics of enterovirus 71 (EV71) strains. Methods A total of 213 cases under 15 years old with AFP were reported by Center for Disease Control and Prevention (CDC) of Yunnan Province of China. Virus isolation was conducted for all samples and the serotypes of isolated NPEV strains were identified by VP1 sequencing. The isolation rates of NPEV in the past consecutive 5 years were analyzed by SPSS22.0 software. Phylogenetic trees of NPEV and EV71 strains were constructed by MEGA6.06 software based on neighbor-joining algorithm and Kimura 2-parameter substitution model and the reliability of the phylogenetic trees was determined by bootstrap analysis with 100 pseudo replicate datasets. Results Altogether, 23 NPEV strains were isolated from 213 AFP cases. Among the 23 strains, 7 strains belonged to EV-A group (2 serotypes, 6 strains of which were EV71), 14 strains belonged to EV-B group (8 serotypes) and the other 2 strains belonged to EV-C group. No NPEV strains of EV-D group were identified. Statistical analysis showed that no significant differences in the isolation rates were observed in the past 5 years (P=0.101). Conclusion The isolation rate of NPEV in patients with AFP in Yunnan province in 2015 was similar to that of the previous years. The EV71 strains of C4 subgenotype were the predominant strains circulating in Yunnan province. Key words: Acute flaccid paralysis; Non-polio enteroviruses; Enterovirus 71; Viral genotyping