Surveillance of enterovirus among acute fluaccid paralysis cases in Beijing, 2013-2017

Abstract

Objective To analyze the characteristics of enterovirus (EV) infections of acute flaccid paralysis (AFP) cases among local and migrant children under 15 years old in Beijing from 2013 to 2017. Methods The demographic data, immunization history, sample collection and testing information, follow-up results and diagnoses of AFP cases in Beijing from 2013 to 2017 were collected from AFP surveillance information report management system. Chi-square test or Fisher's exact probability test was used to describe the differences in detection rates of different types of EV between local and migrant AFP cases. Results A total of 960 AFP cases were reported in Beijing during 2013-2017. EV was detected in 74 samples. The detection rates of EV were 4.0% (7/176) and 8.9% (67/756) for local and migrant AFP cases, respectively and the difference was statistically significant (x2=4.661, P=0.031). The detection rates of polio virus (PV) were 3.4% (6/176) and 3.0% (23/756) (x2=3.48, P=0.062) for local and migrant cases, respectively. The detected PV strains were all polio vaccine strains. These AFP cases had immunization histories of oral polio live attenuated vaccine (OPV) before paralysis and the classification diagnoses were wild polio virus excluded cases. Six cases were diagnosed as vaccine-associated paralytic poliomyelitis (VAPP). The detection rates of non-polio enterovirus (NPEV) were 0.6% (1/176) and 5.8% (44/756) (x2=1.64, P=0.201) for local and migrant cases, respectively. The classification diagnoses of all NPEV cases were wild polio virus excluded cases. Among the 44 migrant NPEV cases, 79.6% was paralyzed during May to September. Conclusions The detection rate of EV among local AFP cases was lower than that among migrant AFP cases reported in Beijing. The classification diagnoses of all AFP cases were wild polio virus excluded cases according to the PV and NPEV detection results. NPEV among migrant AFP cases mainly occurred in summer and autumn. Key words: Poliomyelitis; Poliovirus; Enterovirus; Acute flaccid paralysis