Molecular Epidemiological Analysis Of Hand, Foot, And Mouth Disease In Nanchang And Wuhan

Objective To consturct the persistent surveillance system for HFMD and enterovirus, carry out an epidemiologic and virologic survey of HFMD outbreaks in Jiangxi, Hubei and Henan provinces and offer advise on the prevention, control, diagnosis and treatment of HFMD.Methods Specimens from each HFMD patients were collected and the clinical questionnaire and survey were filled out. Based on these specimens and information, two different sets of analyses were carried out. First, we performed the laboratory procedures, including detection of specimens using RT-PCR, viral isolation, sequencing of VP1region, and full-length genome sequencing of the human enteroviruses isolated. Second, we performed epidemiological analyses with the information from the medical exams, completed surveys, and the laboratory results on the detection and sequencing of specific viruses.Results The main causative agents of HFMD outbreak in Nanchang City from April through May2011was EV71, then was CA16. All the HFMD cases were mild. The peak incidence of HFMD appeared in the age groups of1-4years old and most of them were from home or kindergarten. The number of boys was larger than that of girls. The EV71isolates belonged to C4a cluster and the CA16isolates belonged to B1b cluster. There were two seasonal peaks of HFMD activity during the outbreak of HFMD in Wuhan and nearby cities from April2011through March2012. The peak incidence of HFMD appeared in the age groups of1-3years old and most of them were from home. The number of boys was larger than that of girls. The central nervous system complications were significantly more frequent in patients with EV71infection, but upper respiratory tract infections were significantly more frequent in patients with CA16infection. The EV71isolates belonged to C4a cluster and C4b cluster. C4b spread more widly than C4a. The CA16isolates belonged to Bla cluster and B1b cluster. B1b spread more widly than B1a. The recombination events occurred in three EV71strains isolated from mild and severe cases and the parent strains of them were EV71C4a strain guangdong/GD/CHN/2009and EV71C4b strain SHZH98/GD/CHN/1998.The breakpoints were located at the region of2B-2C junction. The recombination events also occurred in three CA16strains isolated from mild and severe cases and the parent strains of them were CA16genotype A strain FY18/AH/CHN/2008and EV71genotype A strain Hubei-09/HB/CHN/2009.The breakpoint were located at the region of2A-2B junction.Conclusion The epidemic season of HFMD changed owing to different areas and years. The peak incidence of HFMD appeared in the age groups of1-3years old and most of them were from home and kindergarten and we should take these persons as the key object of prevention and control and strengthen their understanding of HFMD. The clinical features of patients with EV71infection were different from that of patients with CA16infecion. EV71C4b reemerged and caused a large-scale HFMD epidemic in Wuhan and nearby cities. Genetic recombination is not sufficient for improving the virulence of EV71and CA16strains.