Circulation of Coxsackievirus A10 and A6 in hand-foot-mouth disease in China, 2009-2011

Abstract

Coxsackieviruses A10 (CV-A10) and A6 (CV-A6) have been associated with increasingly occurred sporadic hand-foot-mouth disease (HFMD) cases and outbreak events globally. However, our understanding of epidemiological and genetic characteristics of these new agents remains far from complete. This study was to explore the circulation of CV-A10 and CV-A6 in HFMD and their genetic characteristics in China. A hospital based surveillance was performed in three heavily inflicted regions with HFMD from March 2009 to August 2011. Feces samples were collected from children with clinical diagnosis of HFMD. The detection and genotyping of enteroviruses was performed by real-time PCR and sequencing of 5'UTR/VP1 regions. Phylogenetic analysis and selection pressure were performed based on the VP1 sequences. Logistic regression model was used to identify the effect of predominant enterovirus serotypes in causing severe HFMD. The results showed 92.0% of 1748 feces samples were detected positive for enterovirus, with the most frequently presented serotypes as EV-71 (944, 54.0%) and CV-A16 (451, 25.8%). CV-A10 and CV-A6 were detected as a sole pathogen in 82 (4.7%) and 44 (2.5%) cases, respectively. Infection with CV-A10 and EV-71 were independently associated with high risk of severe HFMD (OR = 2.66, 95% CI: 1.40-5.06; OR = 4.81, 95% CI: 3.07-7.53), when adjusted for age and sex. Phylogenetic analysis revealed that distinct geographic and temporal origins correlated with the gene clusters based on VP1 sequences. An overall ω value of the VP1 was 0.046 for CV-A10 and 0.047 for CV-A6, and no positively selected site was detected in VP1 of both CV-A10 and CV-A6, indicating that purifying selection shaped the evolution of CV-A10 and CV-A6. Our study demonstrates variety of enterovirus genotypes as viral pathogens in causing HFMD in China. CV-A10 and CV-A6 were co-circulating together with EV-71 and CV-A16 in recent years. CV-A10 infection might also be independently associated with severe HFMD.

Figure 1. The enterovirus type identified in hand-foot-mouth diseases patients during Mar 2009 to Aug 2011, China.

EV, enterovirus; CV, coxsackievirus; ECV, echovirus.

Figure 2. The detailed distribution of enterovirus types in each province.

EV, enterovirus; CV, coxsackievirus; ECV, echovirus.

Figure 3. The temporal distribution of HEV types in hand-foot-mouth diseases patients during March 2009 to August 2011, China.

Figure 4. Phylogenetic trees were constructed from the VP1 nucleotide sequences of CV-A10 using neighbor-joining method with 1000 bootstrap by CLC genomics workbench.

The tree was based on the 379 bp VP1 nucleotide sequences of CV-A10 (nt 2630–3008, responding to AY421767). The strains labeled with green dot were obtained in our study.

Figure 5. Phylogenetic trees were constructed from the VP1 nucleotide sequences of CV-A6 using neighbor-joining method with 1000 bootstrap by CLC genomics workbench.

The tree was based on the 552 bp VP1 nucleotide sequences of CV-A6 (nt 2441–2992, responding to AY421764). The strains labeled with green dot were obtained in our study.