Emerging Enterovirus A71 Subgenogroup B5 Causing Severe Hand, Foot, and Mouth Disease, Vietnam, 2023

Abstract

We report on a 2023 outbreak of severe hand, foot, and mouth disease in southern Vietnam caused by an emerging lineage of enterovirus A71 subgenogroup B5. Affected children were significantly older than those reported during previous outbreaks. The virus should be closely monitored to assess its potential for global dispersal.

Keywords: Vietnam; emerging infections; enteric infections; enterovirus A71; enteroviruses; hand foot and mouth disease; outbreaks; subgenogroup B5; viruses.

Figure 1

Admissions for and severe cases of hand, foot, and mouth disease recorded during January–June 2023 at Children’s Hospital 1, Ho Chi Minh City, Vietnam, in study of emerging enterovirus A71 subgenogroup B5. Green bars indicate total number of patients admitted for hand, foot, and mouth disease. Red bars indicate the number of admitted patients who had severe disease. Numbers above bars indicate actual number of cases at each time point. Scales for the y-axes differ substantially to underscore patterns but do not permit direct comparisons.

Figure 2

Phylogenetic analysis of viral protein 1 (VP1) coding sequences in study of emerging enterovirus A71 subgenogroup B5 causing severe hand, foot, and mouth disease, Vietnam, 2023. Tree was constructed for VP1 gene sequences by using the maximum-likelihood method to compare genetic relatedness among the B5 sequences from this study and global sequences obtained from GenBank. Line colors indicate the country of origin for each sequence. Box colors indicate the enterovirus lineage. Arrow indicates the emerging B5 lineage from Vietnam carrying an S17G codon substitution within the N-terminus of VP1. Similar phylogenetic tree structure was obtained when the analysis was performed by using complete genome coding sequences. Interlineage and intralineage nucleotide sequence similarities among the lineages were calculated (Appendix Table 3). Scale bar indicates nucleotide substitutions per site.