Analysis on the pathogenic characteristics of influenza in Pingliang city of Gansu province, 2009-2017

Objective To reveal the pathogenic characteristics of influenza in the surveillance years during the periods of 2009-2017 in Pingliang city of Gansu province, so as to provide scientific basis for the prevention and control of influenza in the city. Methods The samples from influenza-like illness cases were collected for real-time fluorescent quantitative PCR detection of influenza virus nucleic acids. Cell culture was performed with the canine kidney cell line. The influenza epidemic characteristics were analyzed for time, gender and age distributions. Results For 5 158 surveillance samples, the positive rate of influenza virus nucleic acids was 18.71% (965/5 158), and the proportions of influenza A (H1N1), influenza A (H3N2) and influenza B viruses were 23.79%, 35.99% and 40.22%, respectively. The detection rates of influenza virus in 9 surveillance years were 39.32%, 10.56%, 10.24%, 18.38%, 15.75%, 9.03%, 20.98%, 12.86% and 18.13%, respectively. The incidence rate in 0-6 years old group was the lowest, while the rate in 7-17 years old group was the highest. The differences in the detection rates of nucleic acids by age groups were statistically significant (P<0.05). The influenza virus nucleic acid positive cases were mainly distributed from December to the next March. Ten strains of influenza virus were isolated and the positive rate of isolation was 15.49%. Conclusions The incidences of influenza in Pingliang city were high in winter and spring. The dominant strains of influenza virus were replaced frequently in different years, showing a character of epidemics by mixed dominant strains. The prevention and control measures for influenza in winter and spring should be strengthened. Influenza vaccination should be provided for high risk populations in early September each year. Key words: nfluenza virus; Etiology; Surveillance