Abstract:Objective To study the prevalence of influenza in Chengdu City in 2015, and to analyze the factors influencing influenza surveillance. Methods We collected throat swabs from influenza-like illness (ILI) cases in the sentinel hospitals in Chegndu City in 2015. Influenza viruses were isolated by Madin-Darby cannie kidney (MDCK) cells, and the nucleic acid detected by real-time RT-PCR method. Results The positive rate of influenza viruses was 16.57%, of which the positive rates of influenza A (H1N1), influenza A (H3N2), influenza Victoria-like B virus and influenza Yamagata-like B virus were 0.065%, 11.45%, 0.13% and 4.74% respectively. The coinfection rate of influenza viruses was 0.19%. The coinfection rates of H1+H3, H3+BY and BV+BY were 0.032%, 0.13% and 0.032% respectively. The sensitivity and specificity of real-time RT-PCR method were significantly higher than those of MDCK cell isolation method. The qualified rate of the samples had an impact on the results of virus isolation. Conclutions Influenza A (H3N2) and influenza Yamagata-like B viruses as the superiority strains emerge alternately in Chengdu City in 2015; moreover, co-infection provides the possibility of influenza virus shift. Applying the above-mentioned two methods to detection of influenza viruses, improving the qualities of samples and acquiring the accurate surveillance data are conducive to guiding influenza prevention and control.
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