Etiology of hand, foot and mouth disease and genetic characteristics of prevalent enteroviruses in Qingdao in 2015 / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the etiology of hand,foot and mouth disease (HFMD) and to analyze the genetic characteristics of three prevalent enteroviruses in Qingdao in 2015. Methods City-wide surveillance data in 2015 were used to analyze the epidemiological characteristics of HFMD in Qingdao. RNA samples extracted from throat swab of HFMD cases were examined for general enteroviruses (EVs) such as enterovirus 71(EV71), coxsackievirus A16 (CA16) and CA6 by real-time RT-PCR. Full-length VP1 genes of EV-positive specimens were amplified and sequenced. Sequencing results were phylogenetically analyzed using MEGA 7.0 software package. Results A total of 804 patients with HFMD were identified from 1 176 patients in 2015. CA6 (41.4%),EV71 (31.6%) and CA16 (15.3%) were the predominant EVs causing HFMD. Children 5 years of age and under accounted for 80.3% of the 804 HFMD cases. CA6 was responsible for 48.9% of HFMD cases in children under 3 years old. The epidemic subtypes of EV71 and CA16 in Qingdao were C4a and B1b,respectively. Twenty-eight randomly selected CA6 strains were all classified into type A genome. Conclusion CA6, EV71 and CA16 were the prevalent pathogens causing HFMD in Qingdao in 2015. CA6 became the most predominant pathogen,mainly targeting children under 3 years old. C4a remained the prevailing subtype of EV71,while different from the co-prevalence of B1a and B1b subtypes in the past,B1b became the predominant subtype of CA16. CA6 strains circulating in Qingdao in 2015 mainly belonged to type A genome and evolved into multiple smaller branches. However, CA6 strains isolated in Qingdao in 2015 and 2013 located in different branches.