Spread and evolution of influenza A (H1N1) pdm09 virus in Hubei, 2015–2019

ObjectiveTo understand spread, phylogenetic characteristics, epitope and drug-resistance site of influenza A (H1N1) pdm09 virus in Hubei province during 2015–2019.

MethodsThe spread period of the virus were divided according to the positive rate of influenza virus nucleic acid detection downloaded from influenza surveillance information system in China. Sequencing of 39 strains of influenza A (H1N1) pdm09 virus isolated from the positive samples in real-time fluorescence PCR in Hubei during 2015–2019 was conducted and 13 sequences of the strains isolated from Hubei were downloaded from global influenza database to analyze the distribution of phylogenetic clade, epitope and drug-resistant mutation sites by using bioinformatics software and simulate the structure of mutation sites by 3D modeling.

ResultsThe annual spread of influenza A (H1N1) pdm09 virus lasted for 11–14 weeks in Hubei from 2015 to 2019, and the spread intensity increased year by year. Multiple branches of 6B.1A to 6B.1A7 evolved from 6B clade in phylogenetic tree of the HA and NA genes. Twelve epitope substitutions of HA and two drug-resistance sites of NA were detected, and there were obvious differences in D222G substitution virulence identifying marker and drug-resistance site I223V on homology in 3D modeling structure.

ConclusionThe spread intensity and phylogenetic clade number of influenza A (H1N1) pdm09 virus increased In Hubei during 2015–2019. Sporadic virulence marker and drug-resistance site were detected for influenza A (H1N1) pdm09 virus. The results of this analysis can be used to improve the epidemiological research and genetic evolution surveillance of influenza virus in Hubei.