genetic variation and drug resistance mutation of influenza virus during 2013-2014 in beijing, china: a report of 37 cases

Objective 　To evaluate the evolutionary characteristics of H1N1 and H3N2 influenza A and B viruses, and investigate the drug-resistant mutation of influenza viruses to amantadine and neuraminidase inhibitors (NAIs) during 2013-2014 episode in Beijing. Methods 　RNA was extracted from pharyngeal or nasal swab samples from 37 influenza virus-infected patients and viral genotype/subgenotype were analyzed by real-time reverse-transcription polymerase chain reaction. All influenza A viruses were further directly sequenced for NA and M2 matrix protein (M2) genes, and all influenza B viruses were further sequenced for NA and hemagglutinin (HA) genes. The drug-resistant mutations and genetic evolution were analyzed by Vector NTI software and phylogenetic trees were plotted using Mega software. Results 　Influenza A viruses were identified in 29 patients, including 23 with H1N1 and 6 with H3N2 viruses. Influenza B viruses were identified in 8 patients. M2 gene of all 29 patients with influenza A virus infection were detected with S31N amantadine-resistant mutation. NAIs-resistant mutations were not detected in all 37 patients with influenza A and B virus infection. Phylogenetic analysis showed that HA genes from 5 influenza B virus strains were identified as the B-Yamagata lineage, while NA genes from the corresponding strains were identified as B-Victoria lineage. Conclusions 　Among Beijing Influenza B virus strains reassortants derived from B-Yamagata lineage and B-Victoria lineage were found. DOI: 10.11855/j.issn.0577-7402.2016.02.05