Molecular epidemiology of EV-A71 subgenogroup B5 causing hand, foot and mouth disease in the North, Vietnam, 2012 - 2017

Abstract

Sub - genogroup B5 of EV-A71 (EV-A71_ B5) was co-circulating with EV-A71_C4a to cause outbreak of hand, foot and mouth disease (HFMD) in Northern Vietnam during 2011 and 2012 and then was the most dominant sub - genogroup over the period of 2013 - 2017. There has been limitation in study of
molecular epidemiology for EV-A71_B5 in Northern Vietnam. Therefore, this study aims to describe molecular epidemiology of EVA71 subgenogroup B5 causing hand, foot and mouth disease in the North, Vietnam, 2012 - 2017. Samples of which the clinical specimens were collected under HFMD surveillance programme in Northern Vietnam between 2012 and 2017. It was shown that EV-A71_B5 was detected in most provinces and over the study period but the circulation was spatially and temporally variable. Although 93.5% of EV-A71_B5-associated HFMD patients were moderate, there were 4 severe and fetal cases. Phylogenetic analyis revealed that EV-A71_B5 samples in Northern Vietnam all belonged to Malaysia lineage comprising majority of isolates circulating in a relatively consistent period in the South and the Center of Vietnam and in countries of South - Eastern Asia. Vietnamese EV-A71_B5 samples were further grouped into 5 branches of which the circulation trended to temporally change. The VP1 nucleotide divergence of Vietnames strains was as high as 6.2%, suggesting a diversity of circulating strains. There were unique substitutions detected among Vietnamese strains, including T79A, Y245H and T289S. The variety of origin of imported EV-A71_B5 strains and the diversity of VP1 gene may play important role in their long - term maintanance of endemicity of in Vietnam.