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Intro: Enterovirus-A71 (EV-A71), a major cause of hand, foot, and mouth diseases (HFMD), has caused several outbreaks in Vietnam after its first identification in 2003. In 2011, a large-scale EV-A71 outbreak occurred in Southern Vietnam. To characterize epidemiological patterns of EV-A71 in Southern Vietnam, we conducted a hospital-based enterovirus surveillance in Children's Hospital No. 1 (CH1) Ho Chi Minh City over a 9-year period from 2012- 2020. Methods: Clinical samples (throat swabs and serum) were collected from CH1 inpatients with suspected enteroviruses infection for virus isolation in CH1. VP1- CODEHOP, a molecular assay, was performed for detection and genotyping of enteroviruses in National Health Research Institutes. Full genomes of selected EV-A71 viruses were also sequenced for phylogenetic analysis using Neighbor- joining method in MEGA 11 software. Findings: From 2012 to 2020, a total of 3184 HFMD inpatients were tested and 1693 of them (53%) were positive for enterovirus using VP1-CODEHOP, including 368 (11.56%) EV-A71 cases. Based on virus isolation conducted in 2012-2019, EV-A71 detection rate was 6.79% (177/2607). During the study period, EV-A71 was the top serotype detected in 2013, and 2016∼2018. Overall, the other prevalent serotypes were CV-A2, CV-A6, CV-A10 and CV-A16. Partial VP1 genes of 368 EV-A71 isolates were sequenced, 86.4% were genotype B5 and 13.6% C4. The predominant genotype was C4 in 2012 and shifted to B5 afterward. Based on full genome sequencing of five EV-A71 strains (3 B5 and 2 C4), the genotype C4 viruses were phylogenetically related to the C4 viruses isolated in China, genotype B5 were phylogenetically related to the B5 virus circulated in Malaysia, Singapore, and Taiwan. Conclusion: EV-A71 outbreaks occurred every 2-3 years in Southern Vietnam and the predominant genotype circulating in Southern Vietnam was genotype B5. Development of EV-A71 vaccine is the priority and other prevalent serotypes should be included for developing multivalent vaccines in the future. |
