Abstract
Sporadic HFMD (hand foot and mouth disease, HFMD) cases and outbreaks caused by etiologic agents other than EV71 and CA16 have increased globally. We conducted this study to investigate the prevalence and genetic characteristics of enteroviruses, especially the non-EV71 and non-CA16 enteroviruses, causing HFMD in Shanghai. Clinical specimens were collected from patients with a diagnosis of HFMD. A partial length of VP1 was amplified with RT-PCR and subjected to direct sequencing. Phylogenetic analyses were performed using MEGA 5.0. The ages of the HFMD cases ranged from 3 to 96 months, and the male/female ratio was 1.41. The median hospital stay was 2.96 days. Up to 18.0% of patients had neurologic system complications such as encephalitis, meningoencephalitis or meningitis. Of the 480 samples, 417 were positive for enterovirus (86.9%) with RT-PCR. A total of 13 enterovirus genotypes were identified. The most frequent genotypes were CA6 (31.9%), EV71 (30.6%), CA16 (8.8%) and CA10 (7.5%). Infections with CA6, EV71, CA16 and CA10 were prevalent throughout the years of study, while the proportion of CA6 notably increased from Sep. 2012 to Dec. 2013. Phylogenetic analyses showed that EV71 strains belonged to the C4a subgenogroup and CA16 was identified as B1b subgenogroup. The CA6 strains were assigned to genogroup F, whereas the CA10 strains were assigned to genogroup D. Patients infected with CA6 were typically younger, had a shorter hospital stay and had a lower incidence of neurologic system complications when compared to patients infected with EV71. Our study demonstrates that the enterovirus genotypes causing HFMD were diversified, and there was an increasing prevalence of the non-EV71 and non-CA16 enteroviruses from 2012 to 2013. CA6 was the most predominant pathogen causing HFMD from Sep. 2012 to Dec. 2013, and it often caused relatively mild HFMD symptoms. Most severe HFMD cases were associated with EV71 infection.